PURPOSE: To cause an indoor temperature to coincide with a set temperature at a set hour and to prevent useless consumption of power by a method wherein outdoor and indoor temperatures are detected at specified time before a set hour, a preoperation starting hour is calculated from a difference between a set indoor temperature and an indoor temperature and an outdoor temperature, and operation is started.
CONSTITUTION: When a set hour and an indoor temperature are set, a blower 7 on the indoor side and a blower 8 on the outdoor side are run for a few minutes a specified time before a set hour. Indoor and outdoor temperatures are detected by a temperature sensor 4 on the indoor side and a temperature sensor 9 on the outdoor side and a standard value of an operation starting hour is determined from a difference between detected indoor and outdoor temperatures and an outdoor temperature according to a relational formula. Correction is effected by means of a difference between an indoor temperature and a set value and a preoperation starting hour is set. Operation of an air-conditioner is started at the set hour by means of a microcomputer 2 and control is performed. This constitution performs control so that an indoor temperature is adjusted to a value coinciding with a set indoor temperature at a set hour.