A refrigeration cycle apparatus , comprising a refrigerant circuit , by pipes, connecting a compressor , a flow switching device , a first heat exchanger , an expansion device , and a second heat exchanger , as refrigerant to be circulated through the refrigerant circuit , any one of a refrigerant having saturated gas temperature under standard atmospheric pressure that is higher than that of R32 and a refrigerant mixture mainly composed of the refrigerant being used, the refrigerant circuit including an internal heat exchanger (100-1, 100-2, 100-3) configured to exchange heat between the refrigerant flowing through a first passage connected to a refrigerant inlet of the second heat exchanger and the refrigerant flowing through a second passage connected to a refrigerant outlet of the second heat exchanger , a first extension pipe connecting the first passage and the expansion device , and a second extension pipe connecting the second passage and the flow switching device , the compressor , the flow switching device , and the first heat exchanger being mounted in a heat source-side unit, the second heat exchanger and the internal heat exchanger (100-1, 100-2, 100-3) being mounted in a load-side unit, wherein a bypass mechanism is provided to cause the refrigerant flowing through the refrigerant outlet of the second heat exchanger to bypass the internal heat exchanger (100-1, 100-2, 100-3) in a direction in which the refrigerant flows during an operation in which the second heat exchanger is used as a condenser, and wherein the bypass mechanism includes a bypass pipe connecting the refrigerant inlet and the refrigerant outlet of the second heat exchanger , a first check valve provided on the bypass pipe , and a second check valve provided at an inlet of the internal heat exchanger (100-1, 100-2, 100-3). as refrigerant to be circulated through the refrigerant circuit , any one of a refrigerant having saturated gas temperature under standard atmospheric pressure that is higher than that of R32 and a refrigerant mixture mainly composed of the refrigerant being used, the refrigerant circuit including an internal heat exchanger (100-1, 100-2, 100-3) configured to exchange heat between the refrigerant flowing through a first passage connected to a refrigerant inlet of the second heat exchanger and the refrigerant flowing through a second passage connected to a refrigerant outlet of the second heat exchanger , a first extension pipe connecting the first passage and the expansion device , and a second extension pipe connecting the second passage and the flow switching device , the compressor , the flow switching device , and the first heat exchanger being mounted in a heat source-side unit, the second heat exchanger and the internal heat exchanger (100-1, 100-2, 100-3) being mounted in a load-side unit, wherein a bypass mechanism is provided to cause the refrigerant flowing through the refrigerant outlet of the second heat exchanger to bypass the internal heat exchanger (100-1, 100-2, 100-3) in a direction in which the refrigerant flows during an operation in which the second heat exchanger is used as a condenser, and wherein the bypass mechanism includes a bypass pipe connecting the refrigerant inlet and the refrigerant outlet of the second heat exchanger , a first check valve provided on the bypass pipe , and a second check valve provided at an inlet of the internal heat exchanger (100-1, 100-2, 100-3). wherein the bypass mechanism includes a bypass pipe connecting the refrigerant inlet and the refrigerant outlet of the second heat exchanger , a first check valve provided on the bypass pipe , and a second check valve provided at an inlet of the internal heat exchanger (100-1, 100-2, 100-3). <EOS>