A piston pump is provided with a material compressing cylinder which includes a cylinder chamber with an open rear end, a plunger, a holder for supporting the material compressing cylinder at a slight inclination angle with respect to the center axis of the plunger so that the cylinder head is disposed at the lower side in the gravity direction, a storage chamber for receiving the plunger, a linear drive unit for reciprocating the plunger, an intake port disposed on the head of the material compressing cylinder upward in the gravity direction, and an exhaust port disposed downward in the gravity direction. The storage chamber member is configured that the plunger is drawn into the storage chamber, and the cylinder chamber and the storage chamber are communicated when the reciprocating member of the linear drive unit moves to the terminal end of the stroke.