diff --git a/demo.js b/demo.js
index 82031fd..531de86 100644
--- a/demo.js
+++ b/demo.js
@@ -229,10 +229,13 @@ function renderTable(header, data) {
   return table
 }
 
-function stringify(value) {
-  if (value === undefined) return ''
-  value = toJson(value)
+function stringify(value, depth = 0) {
+  if (value === null) return depth ? 'null' : ''
+  if (value === undefined) return depth ? 'undefined' : ''
+  if (typeof value === 'bigint') return value.toString()
   if (typeof value === 'string') return value
-  if (typeof value === 'object') return JSON.stringify(value)
+  if (Array.isArray(value)) return `[${value.map(v => stringify(v, depth + 1)).join(', ')}]`
+  if (value instanceof Date) return value.toISOString()
+  if (typeof value === 'object') return `{${Object.entries(value).map(([k, v]) => `${k}: ${stringify(v, depth + 1)}`).join(', ')}}`
   return value
 }
diff --git a/src/convert.js b/src/convert.js
index 9108475..d555e6c 100644
--- a/src/convert.js
+++ b/src/convert.js
@@ -66,7 +66,13 @@ export function convert(data, schemaElement, utf8 = true) {
     }
     return arr
   }
-  // TODO: ctype UINT
+  if (ctype === 'UINT_64') {
+    const arr = new BigUint64Array(data.length)
+    for (let i = 0; i < arr.length; i++) {
+      arr[i] = BigInt(data[i])
+    }
+    return arr
+  }
   const logicalType = schemaElement.logical_type?.type
   if (logicalType === 'FLOAT16') {
     return Array.from(data).map(parseFloat16)
diff --git a/src/types.d.ts b/src/types.d.ts
index 3b130b1..70de8e8 100644
--- a/src/types.d.ts
+++ b/src/types.d.ts
@@ -295,6 +295,7 @@ export type DecodedArray =
   Uint8Array |
   Int32Array |
   BigInt64Array |
+  BigUint64Array |
   Float32Array |
   Float64Array |
   any[]
diff --git a/test/files/unsigned.json b/test/files/unsigned.json
new file mode 100644
index 0000000..2a4e727
--- /dev/null
+++ b/test/files/unsigned.json
@@ -0,0 +1,4 @@
+[
+  [0,0,0,0],
+  [255,65535,4294967295,18446744073709552000]
+]
diff --git a/test/files/unsigned.metadata.json b/test/files/unsigned.metadata.json
new file mode 100644
index 0000000..dc6aed3
--- /dev/null
+++ b/test/files/unsigned.metadata.json
@@ -0,0 +1,218 @@
+{
+  "version": 1,
+  "schema": [
+    {
+      "repetition_type": "REQUIRED",
+      "name": "schema",
+      "num_children": 4
+    },
+    {
+      "type": "INT32",
+      "repetition_type": "OPTIONAL",
+      "name": "utiny",
+      "converted_type": "UINT_8",
+      "logical_type": {
+        "type": "INTEGER",
+        "bitWidth": 8,
+        "isSigned": false
+      }
+    },
+    {
+      "type": "INT32",
+      "repetition_type": "OPTIONAL",
+      "name": "usmall",
+      "converted_type": "UINT_16",
+      "logical_type": {
+        "type": "INTEGER",
+        "bitWidth": 16,
+        "isSigned": false
+      }
+    },
+    {
+      "type": "INT64",
+      "repetition_type": "OPTIONAL",
+      "name": "uint"
+    },
+    {
+      "type": "INT64",
+      "repetition_type": "OPTIONAL",
+      "name": "ubig",
+      "converted_type": "UINT_64",
+      "logical_type": {
+        "type": "INTEGER",
+        "bitWidth": 64,
+        "isSigned": false
+      }
+    }
+  ],
+  "num_rows": 2,
+  "row_groups": [
+    {
+      "columns": [
+        {
+          "file_offset": 72,
+          "meta_data": {
+            "type": "INT32",
+            "encodings": [
+              "PLAIN_DICTIONARY",
+              "PLAIN",
+              "RLE"
+            ],
+            "path_in_schema": [
+              "utiny"
+            ],
+            "codec": "SNAPPY",
+            "num_values": 2,
+            "total_uncompressed_size": 64,
+            "total_compressed_size": 68,
+            "data_page_offset": 28,
+            "dictionary_page_offset": 4,
+            "statistics": {
+              "null_count": 0,
+              "max_value": 255,
+              "min_value": 0
+            },
+            "encoding_stats": [
+              {
+                "page_type": "DICTIONARY_PAGE",
+                "encoding": "PLAIN_DICTIONARY",
+                "count": 1
+              },
+              {
+                "page_type": "DATA_PAGE",
+                "encoding": "PLAIN_DICTIONARY",
+                "count": 1
+              }
+            ]
+          }
+        },
+        {
+          "file_offset": 207,
+          "meta_data": {
+            "type": "INT32",
+            "encodings": [
+              "PLAIN_DICTIONARY",
+              "PLAIN",
+              "RLE"
+            ],
+            "path_in_schema": [
+              "usmall"
+            ],
+            "codec": "SNAPPY",
+            "num_values": 2,
+            "total_uncompressed_size": 64,
+            "total_compressed_size": 68,
+            "data_page_offset": 163,
+            "dictionary_page_offset": 139,
+            "statistics": {
+              "null_count": 0,
+              "max_value": 65535,
+              "min_value": 0
+            },
+            "encoding_stats": [
+              {
+                "page_type": "DICTIONARY_PAGE",
+                "encoding": "PLAIN_DICTIONARY",
+                "count": 1
+              },
+              {
+                "page_type": "DATA_PAGE",
+                "encoding": "PLAIN_DICTIONARY",
+                "count": 1
+              }
+            ]
+          }
+        },
+        {
+          "file_offset": 381,
+          "meta_data": {
+            "type": "INT64",
+            "encodings": [
+              "PLAIN_DICTIONARY",
+              "PLAIN",
+              "RLE"
+            ],
+            "path_in_schema": [
+              "uint"
+            ],
+            "codec": "SNAPPY",
+            "num_values": 2,
+            "total_uncompressed_size": 100,
+            "total_compressed_size": 104,
+            "data_page_offset": 309,
+            "dictionary_page_offset": 277,
+            "statistics": {
+              "max": 4294967295,
+              "min": 0,
+              "null_count": 0,
+              "max_value": 4294967295,
+              "min_value": 0
+            },
+            "encoding_stats": [
+              {
+                "page_type": "DICTIONARY_PAGE",
+                "encoding": "PLAIN_DICTIONARY",
+                "count": 1
+              },
+              {
+                "page_type": "DATA_PAGE",
+                "encoding": "PLAIN_DICTIONARY",
+                "count": 1
+              }
+            ]
+          }
+        },
+        {
+          "file_offset": 561,
+          "meta_data": {
+            "type": "INT64",
+            "encodings": [
+              "PLAIN_DICTIONARY",
+              "PLAIN",
+              "RLE"
+            ],
+            "path_in_schema": [
+              "ubig"
+            ],
+            "codec": "SNAPPY",
+            "num_values": 2,
+            "total_uncompressed_size": 80,
+            "total_compressed_size": 84,
+            "data_page_offset": 509,
+            "dictionary_page_offset": 477,
+            "statistics": {
+              "null_count": 0,
+              "max_value": -1,
+              "min_value": 0
+            },
+            "encoding_stats": [
+              {
+                "page_type": "DICTIONARY_PAGE",
+                "encoding": "PLAIN_DICTIONARY",
+                "count": 1
+              },
+              {
+                "page_type": "DATA_PAGE",
+                "encoding": "PLAIN_DICTIONARY",
+                "count": 1
+              }
+            ]
+          }
+        }
+      ],
+      "total_byte_size": 308,
+      "num_rows": 2,
+      "file_offset": 4,
+      "total_compressed_size": 324,
+      "ordinal": 0
+    }
+  ],
+  "key_value_metadata": [
+    {
+      "key": "ARROW:schema",
+      "value": "/////wgBAAAQAAAAAAAKAAwABgAFAAgACgAAAAABBAAMAAAACAAIAAAABAAIAAAABAAAAAQAAACkAAAAZAAAADQAAAAEAAAAfP///wAAAQIQAAAAGAAAAAQAAAAAAAAABAAAAHViaWcAAAAAbv///0AAAACo////AAABAhAAAAAYAAAABAAAAAAAAAAEAAAAdWludAAAAACa////IAAAANT///8AAAECEAAAABgAAAAEAAAAAAAAAAYAAAB1c21hbGwAAMb///8QAAAAEAAUAAgABgAHAAwAAAAQABAAAAAAAAECEAAAABwAAAAEAAAAAAAAAAUAAAB1dGlueQAGAAgABAAGAAAACAAAAAAAAAA="
+    }
+  ],
+  "created_by": "parquet-cpp-arrow version 6.0.1",
+  "metadata_length": 851
+}
diff --git a/test/files/unsigned.parquet b/test/files/unsigned.parquet
new file mode 100644
index 0000000..09d9a2b
Binary files /dev/null and b/test/files/unsigned.parquet differ