To provide a method for controlling an operation capable of reducing the running cost of air conditioning during daytime by executing air-conditioning operation, corresponding to an air conditioning load at night and storing skeleton heat.

In an air-conditioning system, in which an air conditioning route 6 of an indoor side and a heat storage route 8 of a storage heat air passage side are branched and dampers 9 and 10 are provided at the respective routes, a diffusing temperature is controlled constantly for an air conditioning load, when a request for air conditioning at nights is executed, so that the dampers are controlled to be opened or closed, in response to the indoor temperature. The damper 9 of the route is regulated at its opening, so as to become an air flow rate corresponding to the conditioning load, and the damper 10 of the route is regulated at its opening, so as to become the sum of the air flow rates of both the routes of the heat storage and the conditioning becomes constant. Excess power of the air conditioner is utilized as the skeleton heat storage.