A parking brake apparatus may include a parking brake actuator that has a housing that is fixed to a transmission case and a piston including a piston rod, wherein the piston is mounted in the housing to reciprocate along the housing, a lever pivotally coupled to the transmission case, wherein one end portion of the lever is pivotally connected to the piston rod, a sprag rod that is pivotally connected to the other end portion of the lever, and an operational elastic member that is disposed around a rotary shaft of the lever and elastically supports the lever in one rotational direction against the transmission case, wherein the rotary shaft is rotatably coupled to the transmission case.