diff --git a/release_to_gitea.ps1 b/release_to_gitea.ps1
index 15e86f2..d901221 100644
--- a/release_to_gitea.ps1
+++ b/release_to_gitea.ps1
@@ -131,27 +131,20 @@ foreach ($apk in $apkFiles) {
     $mb  = [math]::Round($apk.Length / 1MB, 1)
     Write-Host "  Uploading: $($apk.Name) ($mb MB)..." -ForegroundColor Gray
 
-    $boundary  = [System.Guid]::NewGuid().ToString()
     $uploadUrl = "$GITEA_BASE_URL/api/v1/repos/$GITEA_OWNER/$GITEA_REPO/releases/$($release.id)/assets?name=$($apk.Name)"
 
-    $fileBytes = [System.IO.File]::ReadAllBytes($apk.FullName)
-    $enc       = [System.Text.Encoding]::UTF8
+    # curl.exe (Windows 10+ 内蔵) を使用: WebClient より大容量ファイルに強く、
+    # --max-time で明示的なタイムアウト設定が可能
+    $curlOutput = curl.exe -s --max-time 300 `
+        -X POST $uploadUrl `
+        -H "Authorization: token $GITEA_TOKEN" `
+        -F "attachment=@$($apk.FullName);type=application/octet-stream"
 
-    $bodyParts = [System.Collections.Generic.List[byte]]::new()
-    $header    = "--$boundary`r`nContent-Disposition: form-data; name=`"attachment`"; filename=`"$($apk.Name)`"`r`nContent-Type: application/octet-stream`r`n`r`n"
-    $bodyParts.AddRange($enc.GetBytes($header))
-    $bodyParts.AddRange($fileBytes)
-    $footer = "`r`n--$boundary--`r`n"
-    $bodyParts.AddRange($enc.GetBytes($footer))
-    $bodyArray = $bodyParts.ToArray()
+    if ($LASTEXITCODE -ne 0) {
+        throw "curl upload failed (exit code $LASTEXITCODE)"
+    }
 
-    $wc = New-Object System.Net.WebClient
-    $wc.Headers.Add("Authorization", "token $GITEA_TOKEN")
-    $wc.Headers.Add("Content-Type", "multipart/form-data; boundary=$boundary")
-    $result = $wc.UploadData($uploadUrl, "POST", $bodyArray)
-    $wc.Dispose()
-
-    $json = [System.Text.Encoding]::UTF8.GetString($result) | ConvertFrom-Json
+    $json = $curlOutput | ConvertFrom-Json
     $downloadUrls[$apk.BaseName] = $json.browser_download_url
     Write-Host "  OK: $($json.browser_download_url)" -ForegroundColor Green
 }