By default, Facebook automatically save your search history. It will help you by making it easier for you to find what you are looking for. But, someone will know what you looking for on Facebook if you have been hacked or someone use you computer. You can delete your search history on Facebook and everything will secret.
Step 2, click here and go to History Search in Activity Log
Step 3, click Clear Searches :
Step 4, chose Clear Searches: