To eliminate play of a plunger so as to be able to feed liquid accurately and to prevent excessive force from being imposed on the inside of a pump.

A plunger holding part 41 at the rear end of a plunger 16 is provided with a flange 43 projecting vertically to a plunger shaft. Thrust bearings 44, 45 without ball grooves are interposingly inserted between one face of the flange 43 and the end face of a shaft 42 and between the other face of the flange 43 and a holding member 47, and the holding member 47 and the plunger holding part 41 are energized to the shaft 42 side by springs 26. Axial play of the shaft 42 and plunger 16 is thereby eliminated, and lateral dislocation and slight inclination of the shaft 42 and plunger 16 are allowed, so that excessive force is not imposed on seals 30, 31.