Parking brake of speed changer

Disclosed is a parking brake of a speed changer. The object of the invention is to prevent damage of a parking ratchet and a parking gear due to synchronicity between vibration cycle of the parking ratchet and the rotation speed of the parking gear. When the parking ratchet and the parking gear are jointed, the parking ratchet directly joints with the gear groove of the parking gear and bounces back from the direction opposite to the joint direction. With the bouncing force of a bouncing unit, the parking ratchet reciprocates in an almost fixed vibration cycle. When the vibration cycle of the parking ratchet and the rotation speed of the parking gear are synchronous, the parking ratchet, each time directly jointing with the gear groove of the parking gear, bounces back. Since unequal gear distances of the gear groove of the parking gear are formed, continuous direct joint of the parking ratchet and the gear groove of the parking gear may not occur, thereby preventing the parking ratchet from being violently b