An air conditioning machine comprising: a refrigerant circuit in which a compressor (101, 201), a four-way switching valve, an indoor heat exchanger, an expansion valve (108, 508), and an outdoor heat exchanger are circularly connected; a refrigerant leakage sensing unit that is configured to sense leakage of a flammable refrigerant from the refrigerant circuit; wherein the compressor (101, 201) includes: a cylinder chamber (122, 225); a compression member (129, 179, 240) that is placed in the cylinder chamber (122, 225) and that is configured to compress the flammable refrigerant; and a discharge hole (51a, 251a) through which the flammable refrigerant compressed in the cylinder chamber (122, 225) is discharged, characterized by further comprising: a liquid side on-off valve (111, 311, 411) and a gas side on-off valve (112, 312), the gas side on-off valve being provided between the indoor heat exchanger and the four-way-switching valve; a pump down operation control unit configured to carry out a pump down operation for accumulating the flammable refrigerant in the outdoor heat exchanger when the refrigerant leakage sensing unit senses the leakage of the flammable refrigerant, wherein in the pump down operation a cooling operation is forcibly started, wherein, in the cooling operation, the operation of the compressor is started and the four-way switching valve is switched so that the flammable refrigerant discharged from the compressor in a gas phase flows through the outdoor heat exchanger and the expansion valve becoming the flammable refrigerant in a liquid phase, the liquid side on-off valve (111, 311, 411), through which the flammable refrigerant in the liquid phase flows in the cooling operation, is automatically closed after a lapse of a specified period of time, the gas side on-off valve (112, 312), through which the flammable refrigerant in the gas phase flows in the cooling operation, is automatically closed after a lapse of a specified period of time; and wherein the pump down operation control unit is configured to control the compressor (101, 201) so that the compression member (129, 179, 240) stops at a position where the compression member (129, 179, 240) overlaps at least a portion of the discharge hole (51a, 251a) when viewed in an axial direction of the cylinder chamber (122, 225), at an end of the pump down operation; wherein the liquid side on-off valve (111, 311, 411) is connected between the indoor heat exchanger and the expansion valve. a refrigerant circuit in which a compressor (101, 201), a four-way switching valve, an indoor heat exchanger, an expansion valve (108, 508), and an outdoor heat exchanger are circularly connected; a refrigerant leakage sensing unit that is configured to sense leakage of a flammable refrigerant from the refrigerant circuit; wherein the compressor (101, 201) includes: a cylinder chamber (122, 225); a compression member (129, 179, 240) that is placed in the cylinder chamber (122, 225) and that is configured to compress the flammable refrigerant; and a discharge hole (51a, 251a) through which the flammable refrigerant compressed in the cylinder chamber (122, 225) is discharged, a cylinder chamber (122, 225); a compression member (129, 179, 240) that is placed in the cylinder chamber (122, 225) and that is configured to compress the flammable refrigerant; and a discharge hole (51a, 251a) through which the flammable refrigerant compressed in the cylinder chamber (122, 225) is discharged, a liquid side on-off valve (111, 311, 411) and a gas side on-off valve (112, 312), the gas side on-off valve being provided between the indoor heat exchanger and the four-way-switching valve; a pump down operation control unit configured to carry out a pump down operation for accumulating the flammable refrigerant in the outdoor heat exchanger when the refrigerant leakage sensing unit senses the leakage of the flammable refrigerant, wherein in the pump down operation a cooling operation is forcibly started, wherein, in the cooling operation, the operation of the compressor is started and the four-way switching valve is switched so that the flammable refrigerant discharged from the compressor in a gas phase flows through the outdoor heat exchanger and the expansion valve becoming the flammable refrigerant in a liquid phase, the liquid side on-off valve (111, 311, 411), through which the flammable refrigerant in the liquid phase flows in the cooling operation, is automatically closed after a lapse of a specified period of time, the gas side on-off valve (112, 312), through which the flammable refrigerant in the gas phase flows in the cooling operation, is automatically closed after a lapse of a specified period of time; and wherein the pump down operation control unit is configured to control the compressor (101, 201) so that the compression member (129, 179, 240) stops at a position where the compression member (129, 179, 240) overlaps at least a portion of the discharge hole (51a, 251a) when viewed in an axial direction of the cylinder chamber (122, 225), at an end of the pump down operation; wherein the liquid side on-off valve (111, 311, 411) is connected between the indoor heat exchanger and the expansion valve.