<p>A ventilation system for ventilating spaces and a space adjacent to each of the spaces to efficiently improve comfortableness of the spaces. In an air-conditioning system (100) for performing ventilation by the medium of a common space (CS) and by the use of air of the outside (OS), the ventilation is made for rooms (Ra-Rf) and the common space (CS) contiguous to the rooms (Ra-Rf) with partition plates (Da-Df) in between, respectively. The system has a common space air-conditioner (10) and ceiling-embedded air-conditioner indoor units (20). The common space air-conditioner (10) takes in air of the outside (OS) into the common space (CS). The ceiling-embedded air-conditioner indoor units (20) are arranged corresponding to the rooms (Ra-Rf) on a one-to-one basis and send air in the common space (CS) to the rooms (Ra-Rf). The ceiling-embedded air-conditioner indoor units (20) condition air (CA) of the common space (CS) sent to the rooms (Ra-Rf).</p>
