To provide an air conditioning system that can quickly perform air-conditioning each living room regardless of a distance from the installed place of an air conditioner and improve the ventilation of each living room and moreover supplying air-conditioning air with a small temperature difference from indoor air in a house with high heat insulation and high airtightness.

The air conditioning system includes the air conditioner provided under the floor; an air-conditioning mixing chamber communicating with the air conditioner; air feeding piping that has a blower fan halfway to feed the air-conditioning air to each living room from the air-conditioning mixing chamber; exhaust piping for exhausting indoor air in each living room to the outside; circulating piping for returning the indoor air into a mixing space; and air supply piping supplying outside air into the air conditioner. Air in the air supply piping is conditioned in the air conditioner and then mixed, in the air-conditioning mixing chamber, with the air returned into the mixing space through the circulating piping to become the air-conditioning air, and this air-conditioning air is supplied to each living room through the air feeding piping.