PURPOSE: To improve compression efficiency by a method wherein the valve part of a delivery valve is accurately seated in an adhered state on a seat surface at a delivery port as breakage of a valve and the increase of flow passage resistance or the occurrence of a miss in assembly is prevented.

CONSTITUTION: A delivery valve 5 is formed of a magnetic material and a magnetic force to compensate for adhesion during seating on a seat surface 35 at a delivery port 34 is exerted on the delivery valve 5. Attraction of the delivery valve 5 to the valve press 6 side is prevented from occurring in a way that a non-magnetic thin plate member 8 is located on an opposite surface between the delivery valve 5 and a valve press 6, the valve press 6 is covered with a non-magnetic film 9, or the valve press 6 is formed of a non-magnetic material.