PURPOSE: To work a partition plate certainly and at correct timing in a screw pump provided with a longitudinal groove 3 extending in the axial direction on the inner peripheral surface of a pump outer cylinder 1 as well as providing a screw to rotate in the pump outer cylinder and provided with the above- mentioned partition plate to block between a central shaft 4 and a blade of the adjacent screws to slide in the axial direction in this longitudinal groove 3.
CONSTITUTION: A projection or a roller 22 provided on a partition plate engages with a push-in cam 30 to successively rotate in one direction from above at a push-down position and engages with a push-up cam 32 to rotate successively in one direction from below at a push-down position.