To keep tabs on who is logging in, enable Login Notifications. Each time someone logs in to your account at an unrecognized computer or mobile device, Facebook will alert you via text message or e-mail.

Does Facebook notify when you login from another device?

You can improve the security of your Facebook account by getting an alert when someone tries logging in from a device or web browser we don't recognize. These alerts will tell you which device tried logging in and where it's located.

Does Facebook notify you of a login attempt?

If someone does try to get into your account Facebook will immediately notify you of the attempt and will lock your account. With your account locked Facebook will ask you to review the login attempt. "Someone recently tried to log in to your account from an unrecognized device or mobile device.