To provide a plunger pump well maintainable at all times.

This plunger pump 10 includes a cylinder 11 having a cylinder chamber and a plunger 21 movable forward and backward relative to the cylinder chamber. The cylinder 11 includes an outlet 13 and an inlet 14 which communicate with the cylinder chamber near the front end and which are opposed to each other. Since the plunger 21 includes a cut surface formed on the outer periphery of the front end thereof, the cut surface allows the outlet 13 and the inlet 14 to alternately communicate with the cylinder chamber by the rotating motion and the reciprocating motion of the plunger 21 relative to the cylinder chamber. A fluid can be fed by changing over the communication state. In the plunger pump 10, a groove 23 is formed in the outer peripheral surface of the plunger 21.