According to an article on BuzzFeed.com Facebook stores all your past searches in the Activity Log. But you can only see it if you set your log to "Only Me" visibility. Searches won't ever display on your timeline or profile, and we all know how creepy and stalkerish all of you are. So I’m sure you’d like to know how purge this incriminating evidence from your account. So you don’t get caught with those (Ahem) "questionable" skeletons in your closet or in this case search history.

At first glance it appears that you could only delete your past activity line by line, there is actually is a way to clear all your searches at once. Here’s the rundown

In the left of your Activity Log, click for "More"

BuzzFeed

At the bottom click "Searches"

BuzzFeed

Under "Searches", you'll see the option to "Clear All"

BuzzFeed

Facebook will try to warn you, But you know what to do.

BuzzFeed

[Source:BuzzFeed]