PURPOSE: To enable a valve body and the sliding inner face of a valve casing to have their shaft centers adjusted to each other without deteriorating the function of a suction valve at all and causing any considerable change in the structure of the valve.

CONSTITUTION: A slide tube 40 is interposed between a valve body 36 and a valve guide member 39 and the inner surface of the slide tube 40 and that portion of the inner face of a valve casing 31 where an outlet port 35 is formed are used as sliding faces 41,42 on which the valve body 36 slides and an annular groove 44 is formed in the outer peripheral face of the slide tube 40. An elastic ring 45 made by an 0-ring or the like is mounted in the groove 44 and thereby the slide tube 40 is made to float relative to the valve guide member 39 and the valve body 36 is made to copy the valve casing 31 side of the slid face 42 together with the slide tube 40 and the shift of the slide tube 40 at that time is absorbed by the elastic ring 45.