An anti-theft device for a motorcycle includes an anti-theft locking mechanism, a remote control, a receiver that receives a locking release signal transmitted from the remote control, a controller that releases locking by the locking mechanism according to the locking release signal, and a locking release mechanism that unlocks the locking mechanism by manual operation of a dedicated key. The locking release mechanism is normally covered with a cover member of the motorcycle such that it is not easily detected by unauthorized persons.