Piston pump

According to an aspect of the present invention, there is provided a piston pump (1), comprising: a cylinder (10) formed in a pump body (100); a piston (40) reciprocatable within the cylinder (10); and a seal member (50, 50A) interposed between the cylinder (10) and the piston (40) for sealing fluid tight between a pump chamber (30) and a cam chamber (130), the pump chamber (30) being formed on one end (40a) side of the piston (40) in a sliding direction thereof, the cam chamber (130) being formed on the other end (40b) side of the piston (40) in the sliding direction, wherein the seal member (50, 50A) includes a sliding contact surface (53) closely contactable with the cylinder (10) or the piston (40) and a seal section (L1, L3) to be sealed by the sliding contact surface (53) in the sliding direction of the piston (40), and wherein a length of the seal section (L1, L3) is larger than a stroke length (S1) of the piston (40).