PURPOSE: To enable the optimum control of an air conditioner matching the size and shape of a room, the height of a ceiling, etc.

CONSTITUTION: A control parameter set on the basis of the delay time corresponds to the size and shape of a room, the height of a ceiling, etc., in an air conditioner, to which a device composed of a means 1 measuring and arithmetically operating the starting time of an indoor air blower, a means 2 measuring and arithmetically operating the start time of the change of room temperature and an arithmetic means 3, to which output signals from each means are input and which outputs the delay allowing the optimum control of air-conditioning capacity.