PURPOSE: To improve comfortableness in the reoperation of an air conditioner employing a microcomputer, by storing the time-integrated value of the difference between the temperature of the riding room of an automobile and a set temperature for a predetermined time after the cutoff of main electric power to control the air conditioner on the basis of the stored value at the restarting of the air conditioner.

CONSTITUTION: The temperature 11 of internal air, the temperature 12 of external air and a set temperature 15 are entered into a microcomputer 14 to calculate an aimed blowoff temperature 17 to control actuators 8W10 for the quantity of sent air, internal and external air changeover and door opening degree adjustment through drive circuits 18, 19, a mix door opening degree calculation circuit 20 and a drive circuit 21. The difference between the actual temperature and the aimed blowoff temperature 17 is integrated by an integration circuit 22. A storage circuit 24 and a timer 25 are operated by a main electric power cutoff signal from a power control section 16 to store the result of the integration for a time set by the timer. When restarting is effected within the timer-set time, the stored data 24 are supplied to an aimed blowoff temperature calculator 17 to control the actual blowoff temperature. Comfortableness at the time of restarting is thus improved.