A refrigerant compressor configured by stacking a plurality of compression units 10, 20) and an intermediate partition plate in a direction of a drive shaft, the plurality of compression units (10, 20) being driven by rotation of the drive shaft passing through a center portion, each of the plurality of compression units drawing a refrigerant into a cylinder chamber (11a, 21a) and compressing the refrigerant in the cylinder chamber, and the intermediate partition plate being positioned between the cylinder chamber of one of the plurality of compression units and the cylinder chamber of another one of the plurality of compression units, the refrigerant compressor comprising: - a discharge muffler that defines, as a ring-shaped space around the drive shaft, a discharge muffler space including a discharge port through which the refrigerant compressed at one compression unit of the plurality of compression units (10, 20) is discharged from the cylinder chamber of that compression unit, and a communication port through which the refrigerant discharged through the discharge port flows out to a space located downstream of the one compression unit; - a connecting flow path that passes through the intermediate partition plate in the direction of the drive shaft, and guides the refrigerant from the discharge muffler space through the communication port to the space; and - a communication port flow guide, that covers a predetermined area of an opening portion of the communication port in the discharge muffler space, and characterized by further comprising: a discharge port rear guide that is positioned closer to the discharge port than to the communication port in a flow path in a reverse direction out of two flow paths from the discharge port to the communication port in different directions around the drive shaft in the ring-shaped discharge muffler space, the discharge port rear guide preventing the refrigerant discharged through the discharge port from flowing in the reverse direction, wherein the discharge port rear guide prevents the refrigerant from flowing in the reverse direction, thereby causing the refrigerant to circulate in a forward direction in the ring-shaped discharge muffler space. - a discharge muffler that defines, as a ring-shaped space around the drive shaft, a discharge muffler space including a discharge port through which the refrigerant compressed at one compression unit of the plurality of compression units (10, 20) is discharged from the cylinder chamber of that compression unit, and a communication port through which the refrigerant discharged through the discharge port flows out to a space located downstream of the one compression unit; - a connecting flow path that passes through the intermediate partition plate in the direction of the drive shaft, and guides the refrigerant from the discharge muffler space through the communication port to the space; and - a communication port flow guide, that covers a predetermined area of an opening portion of the communication port in the discharge muffler space, and a discharge port rear guide that is positioned closer to the discharge port than to the communication port in a flow path in a reverse direction out of two flow paths from the discharge port to the communication port in different directions around the drive shaft in the ring-shaped discharge muffler space, the discharge port rear guide preventing the refrigerant discharged through the discharge port from flowing in the reverse direction, wherein the discharge port rear guide prevents the refrigerant from flowing in the reverse direction, thereby causing the refrigerant to circulate in a forward direction in the ring-shaped discharge muffler space.