PURPOSE: To always heat the whole of a food evenly by setting a DUTY for making each feeding time of a micro computer to four magnetrons equal even if any kind of cooking and heating time is set.

CONSTITUTION: With the information of an input device which consists of a cooking selecting key 1, a timer volume 2 and a start key 3 for commanding a start of cooking, a micro computer 12 controls the output of power relays 9A, 9B, 9C, 9D. A timer device 5 for controlling a cooking time determined by the input device and a timer device 7 for controlling ON/OFF of the power relays 9A, 9B, 9C, 9D are comprised. Each feeding time to magnetrons 11A, 11B, 11C, 11D for supplying the high frequency output to a heating chamber 3 can be thereby made equal. As a result, the food is heated evenly.