The present invention relates to a structure for separating oil from a refrigerant gas containing the oil. The refrigerant gas is discharged from a refrigerant compressor which forms a part of refrigerating cycle to an external refrigerant circuit. The oil separation structure includes a separation chamber in which the oil is separated from the discharge refrigerant gas having a cylindrical inner surface, and a plurality of introduction passages through which the discharge refrigerant gas is introduced into the separation chamber. The oil is separated by centrifugal action from the discharge refrigerant gas by turning the discharge refrigerant gas introduced into the separation chamber along the cylindrical inner surface.