PURPOSE: To enable continuous feeding of a food raw material by providing an eccentric shaft which reciprocates a piston according to the rotation of a cylinder to receive a raw material in an opening at an end of the piston hole and extrude the received raw material through an opening at the other end of the piston hole.

CONSTITUTION: A piston 4 is reciprocated in a piston hole 3 according to the rotation of a cylinder 2. The volume of the chamber A is minimized and that of the chamber B is maximized when the eccentric shaft part of the eccentric shaft 7 is inclined to upper right direction by 45°. When the cylinder 2 is further rotated leftward, the piston hole 3 of the cylinder 2 is connected to a feeding port 10, a negative pressure is generated according to the increase of the volume of the chamber A and a raw material is sucked into the chamber A. The sucking and receiving step continues until the chamber A reaches the lower left position by the further rotation of the cylinder 2 and is finished when the chamber A is disconnected from the feeding port 10. When the chamber A passes the position inclined to lower left direction by 45°, the raw material in the chamber A is transferred toward the extrusion port 11 and delivered under pressure.