Oil supply grooves (74, 84) are formed respectively in a rotating shaft (70) of a compression mechanism (50) integral with an electric motor (40) and in a rotating shaft (80) of an expansion mechanism (60). The rotating shafts (70, 80) are coupled together by engagement between an engagement convex portion (85) and an engagement concave portion (75) which are formed respectively in shaft ends of the rotating shafts (70, 80). And, a seal groove (S) is formed in the peripheral surface of the engagement convex portion (85) and an O-ring (R) is engaged into the seal groove (S). Hereby, lubrication oil leakage from between the engagement convex portion (85) and the engagement concave portion (75) is prevented.