PURPOSE: To reduce cost of a humidifying system and further contrive its energy caving.

CONSTITUTION: Each of air conditioning devices 5a, 5b... disposed for each of a plurality of rooms 2a, 2b... is provided with steam atomization nozzles 6a, 6b..., and each of the steam atomization nozzles 6a, 6b... and a single steam producing device 10 are connected through each of opening or closing solenoid valves 9a, 9b,.... Each of the opening or closing solenoid valves 9a, 9b... is controlled by a control circuit 12 under a time sharing operation for its opening or closing operation and steam from the steam producing device 10 is supplied to each of the rooms 2a, 2b... under a time sharing condition so as to humidify each of the rooms.