diff --git a/app/services/line/send_on_line_service.rb b/app/services/line/send_on_line_service.rb
index b0b6d828d..3c9d6cf17 100644
--- a/app/services/line/send_on_line_service.rb
+++ b/app/services/line/send_on_line_service.rb
@@ -44,10 +44,15 @@ class Line::SendOnLineService < Base::SendOnChannelService
       # Support only image and video for now, https://developers.line.biz/en/reference/messaging-api/#image-message
       next unless attachment.file_type == 'image' || attachment.file_type == 'video'
 
+      # Use file_url (permanent redirect-based URL) instead of download_url (signed URL that expires in 5 minutes).
+      # LINE mobile app lazy-loads images and may fetch them well after the message is sent.
+      original_url = attachment.file_url
+      preview_url = attachment.thumb_url.presence || original_url
+
       {
         type: attachment.file_type,
-        originalContentUrl: attachment.download_url,
-        previewImageUrl: attachment.download_url
+        originalContentUrl: original_url,
+        previewImageUrl: preview_url
       }
     end
   end
diff --git a/spec/services/line/send_on_line_service_spec.rb b/spec/services/line/send_on_line_service_spec.rb
index a7520b8d8..4451a53b9 100644
--- a/spec/services/line/send_on_line_service_spec.rb
+++ b/spec/services/line/send_on_line_service_spec.rb
@@ -161,7 +161,9 @@ describe Line::SendOnLineService do
       it 'sends the message with text and attachments' do
         attachment = message.attachments.new(account_id: message.account_id, file_type: :image)
         attachment.file.attach(io: Rails.root.join('spec/assets/avatar.png').open, filename: 'avatar.png', content_type: 'image/png')
-        expected_url_regex = %r{rails/active_storage/disk/[a-zA-Z0-9=_\-+]+/avatar\.png}
+        attachment.save!
+        expected_original_url_regex = %r{rails/active_storage/blobs/redirect/[a-zA-Z0-9=_\-+]+/avatar\.png}
+        expected_preview_url_regex = %r{rails/active_storage/representations/redirect/[a-zA-Z0-9=_\-+]+/[a-zA-Z0-9=_\-+]+/avatar\.png}
 
         expect(line_client).to receive(:push_message).with(
           message.conversation.contact_inbox.source_id,
@@ -169,8 +171,8 @@ describe Line::SendOnLineService do
             { type: 'text', text: message.content },
             {
               type: 'image',
-              originalContentUrl: match(expected_url_regex),
-              previewImageUrl: match(expected_url_regex)
+              originalContentUrl: match(expected_original_url_regex),
+              previewImageUrl: match(expected_preview_url_regex)
             }
           ]
         )
@@ -181,16 +183,18 @@ describe Line::SendOnLineService do
       it 'sends the message with attachments only' do
         attachment = message.attachments.new(account_id: message.account_id, file_type: :image)
         attachment.file.attach(io: Rails.root.join('spec/assets/avatar.png').open, filename: 'avatar.png', content_type: 'image/png')
+        attachment.save!
         message.update!(content: nil)
-        expected_url_regex = %r{rails/active_storage/disk/[a-zA-Z0-9=_\-+]+/avatar\.png}
+        expected_original_url_regex = %r{rails/active_storage/blobs/redirect/[a-zA-Z0-9=_\-+]+/avatar\.png}
+        expected_preview_url_regex = %r{rails/active_storage/representations/redirect/[a-zA-Z0-9=_\-+]+/[a-zA-Z0-9=_\-+]+/avatar\.png}
 
         expect(line_client).to receive(:push_message).with(
           message.conversation.contact_inbox.source_id,
           [
             {
               type: 'image',
-              originalContentUrl: match(expected_url_regex),
-              previewImageUrl: match(expected_url_regex)
+              originalContentUrl: match(expected_original_url_regex),
+              previewImageUrl: match(expected_preview_url_regex)
             }
           ]
         )