To provide an efficient piston pump having a small number of parts and simple assembly steps, and consuming less current in achieving a relatively low ultimate pressure. The piston pump comprises: a suction port (28) through which gas sucked by varying the volume of a pump chamber (22) defined by a cylinder (12) and a piston (14) fitted in the cylinder (12) passes as the piston (14) is reciprocated, an exhaust port (20) through which the gas discharged by varying the volume of the pump chamber (22) passes, a suction valve (26) installed in the suction port (28) disposed on a piston top, and an exhaust valve (18) installed in the exhaust port (20) disposed on a top of the cylinder (12).