An air conditioner comprising: an indoor (40a, 40b, 40c) including an indoor heat exchanger (41a, 41b, 41c), an outdoor including an outdoor heat exchanger and a compressor for compressing a refrigerant, a liquid pipe through which the refrigerant liquefied by one of the outdoor heat exchanger and the indoor heat exchanger (41a, 41b, 41c) is enabled to flow from the one of the outdoor heat exchanger and the indoor heat exchanger (41a, 41b, 41c) to the other one of the outdoor heat exchanger and the indoor heat exchanger (41a, 41b, 41c), and a high or low pressure gas pipe through which the refrigerant is enabled to flow between the compressor and the indoor heat exchanger (41a, 41b, 41c) while being prevented from passing through the outdoor heat exchanger, characterized in that the outdoor further includes: a first four-way valve including a first high pressure port through which the compressed refrigerant is enabled to be taken from the compressor into the first four-way valve, a first low pressure port through which the refrigerant is enabled to be taken from the first four-way valve into the compressor, a heat exchanger port through which the refrigerant is enabled to flow between the outdoor heat exchanger and the compressor, and a first dead port fluidly connected to the first high pressure port when the refrigerant flows from the heat exchanger port to the first low pressure port and fluidly connected to the first low pressure port when the refrigerant flows from the first high pressure port to the heat exchanger port, a second four-way valve including a second high pressure port through which the compressed refrigerant is enabled to be taken from the compressor into the second four-way valve, a second low pressure port through which the refrigerant is enabled to be taken from the second four-way valve into the compressor, a high or low pressure gas pipe port through which the refrigerant is enabled to flow between the high or low pressure gas pipe and the compressor, and a second dead port fluidly connected to the second high pressure port when the refrigerant flows from the high or low pressure gas pipe port to the second low pressure port and fluidly connected to the second low pressure port when the refrigerant flows from the second high pressure port to the high or low pressure gas pipe port, a first capillary tube allowing a fluidal flow between the second dead port and the refrigerant between the heat exchanger port and the outdoor heat exchanger, and a second capillary tube allowing a fluidal flow between the first dead port and the high or low pressure gas pipe. a first four-way valve including a first high pressure port through which the compressed refrigerant is enabled to be taken from the compressor into the first four-way valve, a first low pressure port through which the refrigerant is enabled to be taken from the first four-way valve into the compressor, a heat exchanger port through which the refrigerant is enabled to flow between the outdoor heat exchanger and the compressor, and a first dead port fluidly connected to the first high pressure port when the refrigerant flows from the heat exchanger port to the first low pressure port and fluidly connected to the first low pressure port when the refrigerant flows from the first high pressure port to the heat exchanger port, a second four-way valve including a second high pressure port through which the compressed refrigerant is enabled to be taken from the compressor into the second four-way valve, a second low pressure port through which the refrigerant is enabled to be taken from the second four-way valve into the compressor, a high or low pressure gas pipe port through which the refrigerant is enabled to flow between the high or low pressure gas pipe and the compressor, and a second dead port fluidly connected to the second high pressure port when the refrigerant flows from the high or low pressure gas pipe port to the second low pressure port and fluidly connected to the second low pressure port when the refrigerant flows from the second high pressure port to the high or low pressure gas pipe port, a first capillary tube allowing a fluidal flow between the second dead port and the refrigerant between the heat exchanger port and the outdoor heat exchanger, and a second capillary tube allowing a fluidal flow between the first dead port and the high or low pressure gas pipe.