To set an interior machinery, an exterior machinery and a piping by preventing intrusion of air into the piping at the time of installing and remov ing the interior machinery and the exterior machinery, preventing emission of refrigerant gas in the air and without gas charging.

Height positions (setting positions) of an interior machinery 1 and an exterior machinery 4 are made roughly the same by arranging the exterior machinery 4 on a fixed piece 97 fixed on a side surface of a wall 93. One receptacle 51 of a self-sealing type double pipe coupler 10 is connected to the side of the interior machinery 1, and the other plug 11 of the self-sealing type double pipe coupler 10 is connected to a head end of a piping 100 constituted of a high pressure pipe and a low pressure pipe from the side of the exterior machinery 4. Installation of an air conditioner is finished only by connecting the receptacle 51 and the plug 11 on the side of the interior machinery 1, and it is possible to separate the interior machinery 1 and the exterior machinery 4 without leaking refrigerant gas in the air only by removing the receptacle 51 and the plug 11 even in the case of removing it.