Abstract: This invention provides a piston pump in which a cylinder block is provided with a plurality of cylindrical apertures arranged radially with a tilt angle and a plurality of pistons are slidably inserted into each cylindrical aperture of the cylinder block and are held between the cylinder block and a cylindrical holder which is in contact with the outer end face of each piston. The cylinder block is rotatably fitted on the conical periphery of a slidable truncated conical pintle which is held eccentrically from the center of a driven shaft for rotating the cylinder block and the cylindrical holder together therewith. Thus, each piston can be reciprocated for pumping action by rotating the cylinder block together with the cylindrical holder around the conical periphery of the pintle so that each piston can suction up fluid through an arcuate groove formed on the conical periphery of the pintle and communicates with an inlet passage.