An inlet port 15 is divided into a plurality of holes 15a, 15b, 15c, 15 by ribs 61a, 61b, 61c. For example, when liquid refrigerant is compressed within a compression chamber, the inlet valve 21 receives excessive load which is about to bend the inlet valve 21 largely toward the suction chamber side. However, the inlet valve 21 is supported by the ribs 61a, 61b, 61c, and therefore the inlet valve 21 is hardly bent, but the inlet port 21 is positively closed.