A hydraulic pump of a driving force distribution apparatus for right and left axles includes a pump shaft, a swash plate supported tiltably, swash plate tilting and holding mechanism unit for tilting and holding the swash plate to one side or to the other side depending on the direction of rotation of the pump shaft, and a hydraulic oil supply mechanism unit having a cylinder block. The cylinder block holds pistons which reciprocate inside cylinder holes while making contact with a tilt surface of the swash plate at their extremities. When the pump shaft rotates in a forward or reverse direction, the pistons reciprocate to supply hydraulic oil sucked from a tank to a suction port of an operation control valve. Thus, the driving force distribution apparatus can apply relative rotating forces to right and left axles even during backward running, with no increase in the size of the apparatus.