An accumulator comprising: a tank having an inlet port and an outlet port; an outlet pipe provided within the tank, the outlet pipe being coupled at one end to the outlet port and being open at another end inside of the tank; and a gas-liquid separator adapted to separate a refrigerant introduced into the tank via the inlet port into a liquid-phase refrigerant and a gas-phase refrigerant, wherein: a floating member is disposed on an outer periphery of the outlet pipe so as to be slidable in a vertical direction, the floating member being adapted to move up or down and being provided with an oil return hole in a portion to be immersed in the oil, and the outlet pipe is provided with a slit hole extending in the vertical direction and being adapted to be continuous with the oil return hole when the oil surface level exceeds a predetermined level, wherein the floating member includes a cylindrical sliding portion externally arranged around the outlet pipe so as to be slidable and a plate-like flange portion extending outwardly from the sliding portion, characterized in that the floating member being adapted to move up or down according to change in an oil surface level with buoyancy received from oil included in the refrigerant, and the oil return hole is provided in a lower portion of the sliding portion with respect to the flange portion. a tank having an inlet port and an outlet port; an outlet pipe provided within the tank, the outlet pipe being coupled at one end to the outlet port and being open at another end inside of the tank; and a gas-liquid separator adapted to separate a refrigerant introduced into the tank via the inlet port into a liquid-phase refrigerant and a gas-phase refrigerant, wherein: a floating member is disposed on an outer periphery of the outlet pipe so as to be slidable in a vertical direction, the floating member being adapted to move up or down and being provided with an oil return hole in a portion to be immersed in the oil, and the outlet pipe is provided with a slit hole extending in the vertical direction and being adapted to be continuous with the oil return hole when the oil surface level exceeds a predetermined level, wherein the floating member includes a cylindrical sliding portion externally arranged around the outlet pipe so as to be slidable and a plate-like flange portion extending outwardly from the sliding portion, characterized in that the floating member being adapted to move up or down according to change in an oil surface level with buoyancy received from oil included in the refrigerant, and the oil return hole is provided in a lower portion of the sliding portion with respect to the flange portion. a floating member is disposed on an outer periphery of the outlet pipe so as to be slidable in a vertical direction, the floating member being adapted to move up or down and being provided with an oil return hole in a portion to be immersed in the oil, and the outlet pipe is provided with a slit hole extending in the vertical direction and being adapted to be continuous with the oil return hole when the oil surface level exceeds a predetermined level, wherein the floating member includes a cylindrical sliding portion externally arranged around the outlet pipe so as to be slidable and a plate-like flange portion extending outwardly from the sliding portion, characterized in that the floating member being adapted to move up or down according to change in an oil surface level with buoyancy received from oil included in the refrigerant, and the oil return hole is provided in a lower portion of the sliding portion with respect to the flange portion.