A parking brake apparatus including a bolt screw rotated by a driving force transmitted from an actuator, one or more pistons disposed at one side or both sides of the bolt screw, one or more screw nuts accommodated in the piston, screwed to an end of the bolt screw, and moved along with the rotation of the bolt screw, one or more elastic members disposed around the screw nut within the piston, and elastically deformed, in response to a displacement of the screw nut while the screw nut is moved by a set distance, to press the piston toward a shoe, and a load transfer unit disposed in the piston, and configured to transmit, to the piston, a displacement of the screw nut when the screw nut moves more than the set distance, thereby pressing the piston toward the shoe.