PURPOSE: To prevent malodor in a lavatory zone from backwardly flowing into a dressing zone or from flowing into a common space by providing an exhaust port in each of the lavatory zone and the dressing zone, and controlling the ventilation such that the number of times of ventilation for the lavatory zone is more increased than that for the dressing zone.

CONSTITUTION: Exhaust ports are provided in a ceiling in a lavatory room 1. The exhaust 31 in a lavatory zone 7 and an exhaust port 32 in a dressing zone 8 are individually provided. The number of times of ventilation from the exhaust port 31 of the lavatory zone 7 by driving a ventilating fan 37 and that from the exhaust port 32 of the dressing zone 8 by driving a ventilating fan 38 are different from each other. The number of times of ventilation for the lavatory zone 7 is more increased than that for the dressing zone as described above, whereby a pressure difference is produced between the lavatory zone and the dressing zone 8 to permit air on the side of the dressing zone 8 to flow into the side of the lavatory zone 7. Thus, any bad odor on the side of the lavatory zone 7 is prevented from backwardly flowing into the side of the dressing zone 8.