PURPOSE: To permit demand control while effecting air conditioning, by a method wherein the changing operation of setting in respective air-conditioning machine is effected by the demand means of a central unit so that the set temperature of the air-conditioning machine under operation is raised by 1°C upon cooling while the set temperature of the same is reduced by 1°C upon heating when amount of electric power for the air-conditioning machine has exceeded the specified value of an upper limit.

CONSTITUTION: When the amount of electric power is increased and has exceeded the specified value of an upper limit, a command is outputted from a central unit 1 to an air-conditioning machine control means 6 in a controller 7 so as to raise the set temperature of the air- conditioning machine 3 under operation by 1°C and, thus, the change of the set temperature is effected. When the amount of electric power is not reduced to a value lower than the specified value of a lower limit after a given period of time has elapsed, the set temperature is raised continuously by 1°C in the same manner and this control is repeated until the amount of electric power becomes lower than the specified value of the lower limit. The set temperature is shifted in such a manner whereby a difference between an indoor temperature and the set temperature is reduced and the compressor 8 of the air-conditioning machine 3, whose air-conditioning load is small among a plurality of air-conditioning machines 3, repeats the ON-OFF operation thereof by a room temperature control function, therefore, the amount of electric power is reduced and demand control may be effected.