To provide a multiroom air conditioner by which the construction between rooms produced at a factory can be performed easily, with simple constitution.

A heat source machine 1 to produce cold water is installed, and also rooms to be coupled on the site of erection are produced at the factory, and an indoor terminal 2 to perform air conditioning action is installed in the room at the factory. Moreover, the heat source 1 and the indoor terminal 2 are connected with each other, and a part of pipe lines 3 and 4 to circulate cold/hot water is installed in the room at the factory. Hereby, when coupling the rooms produced at the factory with one another on the site of erection, the pipe lines such as the supply pipe lines 3 installed in advance in the room, return pipe lines 4, etc., can be connected with one another easily and normally, and the work time can be shortened, and the cost can be reduced. Moreover, since the pipe lines 3 and 4 are installed in advance in the room, the indoor terminals 2 can be added easily, and the facility extendability improves.