A steering lock device includes a main frame, a lock insertion hole formed on the main frame, a lock member slidably disposed in the lock insertion hole, a pin insertion portion formed on the lock member, a stopper housing portion formed on the main frame, a stopper pin housed in the stopper housing portion, and a trigger detachably disposed on the main frame. The stopper pin is urged toward a latch position by a stopper, and engaged, in a state of positioning at the latch position, with the pin insertion portion of the lock member positioning at the lock position. The trigger holds, in a state of being attached on the main frame, the stopper pin at an unlatch position by contacting with the stopper pin. First stepped portions for engaging with the stopper pin positioning at the latch position are disposed in a side of the unlock position, around an opening of the stopper housing portion and on a wall surface of the lock insertion hole facing to the opening. Since the lock member is firmly held at the lock position by the stopper pin even if a cover or a coil spring urging the lock member is removed, an improper unlock of the lock member can be prevented.