1. Go to your ‘Account settings’

Link: https://www.facebook.com/deactivate.php (step 3)

2. Click on ‘Security’ and then on ‘Deactivate your account’.

Link: https://www.facebook.com/deactivate.php  (step 3)

3. Click on the ‘Confirm’ button

Link: https://www.facebook.com/deactivate.php

Done: Your facebook is now deactivated.

Important, when you login again, your account will be activated.