An air conditioner includes an outdoor heat exchanger configured to exchange heat between a refrigerant and outdoor air; an indoor heat exchanger configured to exchange heat between the refrigerant and indoor air; a first pipe configured to provide a channel for the refrigerant flowing out of the outdoor heat exchanger and having a first inner diameter; a second pipe configured to provide a channel for the refrigerant flowing into the indoor heat exchanger; a coupling member configured to couple end portions of the first pipe and the second pipe; and a first insertion pipe inserted in the second pipe at the end portion of the second pipe and having a second inner diameter smaller than the first inner diameter of the first pipe.