A swash-plate type piston pump includes a cylinder block configured to be rotated with rotation of a driving shaft, a plurality of pistons accommodated in a plurality of cylinders provided in the cylinder block, a swash plate configured to reciprocate the piston so that a volume chamber of the cylinder is expanded/contracted with the rotation of the cylinder block, an biasing mechanism configured to bias the swash plate in a direction where a tilting angle is made larger, a control pin configured to drive the swash plate in a direction where the tilting angle is made smaller in accordance with a rise in a load pressure of a pressure chamber, and a discharge channel configured to discharge the load pressure of the pressure chamber.