A piston pump including a pump housing, a piston provided at the inner bore of the pump housing and assembled with an annular sealing member to form a pump chamber. The piston is configured to slide at an inner wall of the inner bore. The annular sealing member is assembled with the piston so as to slide at the inner wall of the inner bore in the axial direction together with the piston. And a first sliding range of the piston relative to the inner wall of the inner bore and a second sliding range of the annular sealing member relative to the inner wall of the inner bore do not overlap each other in the axial direction.