A bicycle lock comprises a handlebar union connecting a handlebar with a bicycle frame and having an insert hole; a lock mechanism built in the handlebar union and manipulated to have a lock state or an unlock state; and a cable with one end thereof connected with the handlebar union and another end thereof having a bolt. The cable can be wound around a fixed object. The bolt can be inserted into the insert hole and manipulated to a lock state via the lock mechanism to make the bolt neither disengage from the insert hole nor separate from the handlebar union.