To improve sealability of a device in which a fixed scroll member and a casing have sealing surfaces to be engaged with each other by forming screw holes on recessed seal surfaces a plate body composing a discharge chamber for fixing the fixed scroll member to the casing through screw-s.

A scroll compressor has a fixed scroll member 9 and a movable scroll member 10 in a space between a casing 1 and a shaft supporting part. In such a scroll compressor, the fixed scroll member 9 is threadedly fastened by inserting screws 11 into four screw holes 9a formed on a plate body 13, and surface-sealed. Projected seal surfaces A and recessed seal surfaces B are formed on the sealing surface of the plate body 13 so as to form a continuous curved surface in the circumferential direction. The screw holes 9a are formed only on the recessed seal surfaces B. The recessed seal surfaces B are pulled to the side of a stepped portion 1a by screwing. Both the seal surfaces A and B show almost flat state, so that even and certain surface sealing condition is obtained.