Disclosed herein is an auxiliary apparatus of a carrier mounted to a rear portion of a vehicle, including a locking unit fastened to the carrier, the locking unit including a locking pin to be extracted or retracted in response to operation of a switch unit, a rotary plate rotatably coupled to the locking unit, and a fastening member mounted to the rotary plate, the fastening member having at least a fastening hole into which the locking pin is selectively inserted and locked according to the operation of the switch unit.