To permit economical operation without providing only a specified air conditioner with a load by a method wherein respective air conditioners are controlled individually by an integrated controller, connected to respective air conditioners, in accordance with respective counter values.

Clean rooms 1, 2 are provided with air conditioners 5, 6, arranged individually in an air conditioner room 3, and counters 8, arranged in each clean rooms 1, 2. The detected values of respective particle counters 8 are inputted into an integrated controller 9, arranged in a control chamber 4. The integrated controller 9 monitors the detecting values of respective particle counters 8 and controls respective air conditioners 5, 6 individually based on the detecting values. According to this method, economical operation can be effected without providing only a specified air conditioner with a load.