Do you want to delete a particular message on Facebook? If yes then you can delete it without deleting the whole conversation.
At first log into your Facebook account and click on “Messages” from the left.
Now select the person whose message you want to delete.
You will see the list of conversation on the right.
Click on “Actions” button and select “Delete Messages“.
You will see check boxes appear in front of all the messages. Select the check-box in front of the message which you want to delete and click on “Delete” button.
You will be informed that once you delete the message than you can’t retrieve it.
Click on “Delete messages” if you want to delete it or else click “Cancel“.
This is how you can delete a message on Facebook.