PURPOSE: To enable a very small amount of a liquid to be fed with no pulsation without a check valve being arranged, by operating three piston pumps with cams shifted by 120deg. from each other and made in synchronism with a cam shaft which is rotatably driven by a motor.

CONSTITUTION: Piston 3a through 3c are made contact, under pressing force by springs 4a through 4c, with cams 5a through 5c which are shifted by 120deg. from each other and are secured onto a cam shaft 6 rotatary driven by a motor 7. Accordingly, liquid may be sequentially fed from piston pumps P1 through P3 every one-third of rotation, thereby the liquid may be fed with no pulsation even without a check valve being arranged.