To provide a balcony whose space can be used widely.

An exterior wall panel 24 to which a large number of vent holes 23 are formed is installed onto one side face of the balcony, a housing chamber 22 in which a front on the reverse side to the exterior wall panel is opened while an outdoor machine 21 is housed is mounted inside the exterior wall panel 24, and a cover panel 27 to which a large number of the vent holes 28 are formed is set up into the opening in an openable and closeable manner. A fixed space is formed in front of the cover panel 27 while the outdoor machine 21 is supplied with air through the vent holes 28 of the cover panel 27, and the outdoor machine 21 is exhausted through the vent holes 23 of the exterior wall panel 24.