A clothes dryer, comprising: - a body (100, 300, 410); - a tub (110, 310, 420) rotatably installed in the body (100, 300, 410); - a suction duct (120, 370, 430) installed at the body (100, 300, 410), and configured to suck external air and to supply the external air into the tub (110, 310, 420); and - an exhaustion duct (140, 360, 450) configured to exhaust a part of the air having passed through the tub (110, 310, 420) to outside of the body (100, 300, 410); - a heat pump having a first heat exchanger (130, 340, 440) for heating air, a second heat exchanger (135, 330, 460) for cooling air, a compressor (150, 350, 470) and an expander connected between the first and second heat exchangers (130, 340, 440; 135, 330, 460) by pipes, characterized by - a bypass duct (145, 360a) provided with flow control means (146, 365) to control the amount of air which participates in heat exchange in the second heat exchanger (135, 330, 460) based on the amount of air which can be processed by the heat pump, the bypass duct (145, 360a) having one end communicated with outside of the body and another end communicated with an upstream side of the second heat exchanger (135, 330, 460) at the exhaustion duct (140, 360, 450) or having the another end communicated with a circulation duct configured to re-supply part of the air passing through the exhaustion duct (140, 360) into the tub (310, 420) through circulation and diverged from the exhaustion duct (140, 360, 450); - wherein the second heat exchanger (135, 330, 460) is configured to heat-exchange with a part of the air passing through the exhaustion duct (140, 360, 450) for recovering waste heat, - wherein the first heat exchanger (130, 440) is installed on a flow path of the suction duct (120, 430) and the second heat exchanger (135, 460) is installed on a flow path of the exhaustion duct (140, 450); or - wherein the first and the second heat exchangers (330, 340; 460, 440) are sequentially installed on a flow path formed by the circulation duct. - a body (100, 300, 410); - a tub (110, 310, 420) rotatably installed in the body (100, 300, 410); - a suction duct (120, 370, 430) installed at the body (100, 300, 410), and configured to suck external air and to supply the external air into the tub (110, 310, 420); and - an exhaustion duct (140, 360, 450) configured to exhaust a part of the air having passed through the tub (110, 310, 420) to outside of the body (100, 300, 410); - a heat pump having a first heat exchanger (130, 340, 440) for heating air, a second heat exchanger (135, 330, 460) for cooling air, a compressor (150, 350, 470) and an expander connected between the first and second heat exchangers (130, 340, 440; 135, 330, 460) by pipes, - a bypass duct (145, 360a) provided with flow control means (146, 365) to control the amount of air which participates in heat exchange in the second heat exchanger (135, 330, 460) based on the amount of air which can be processed by the heat pump, the bypass duct (145, 360a) having one end communicated with outside of the body and another end communicated with an upstream side of the second heat exchanger (135, 330, 460) at the exhaustion duct (140, 360, 450) or having the another end communicated with a circulation duct configured to re-supply part of the air passing through the exhaustion duct (140, 360) into the tub (310, 420) through circulation and diverged from the exhaustion duct (140, 360, 450); - wherein the second heat exchanger (135, 330, 460) is configured to heat-exchange with a part of the air passing through the exhaustion duct (140, 360, 450) for recovering waste heat, - wherein the first heat exchanger (130, 440) is installed on a flow path of the suction duct (120, 430) and the second heat exchanger (135, 460) is installed on a flow path of the exhaustion duct (140, 450); or - wherein the first and the second heat exchangers (330, 340; 460, 440) are sequentially installed on a flow path formed by the circulation duct.