A pedal is switched between a normal position and a low position, which is reached by depressing the pedal downward from the normal position with toes of a foot of a user. A pedal locking unit switches the pedal between a locked state in which the pedal is locked at the low position and an unlocked state in which the pedal is released from the locked state. A lock switch plate switches the pedal locking unit to the locked state. An unlock switch plate releases the pedal from the locked state of the pedal locking means. The lock and unlock switch plates are located beside the pedal to be operable by a heel of the foot.