PURPOSE: To improve the detection accuracy on steam and like by a finishing sensor and consequently enable to automatically cook food in optimum heating sequence by microwaves by a method wherein air blown into an oven is stopped over the period of time where no microwaves are generated.

CONSTITUTION: A central control circuit 20 automatically cooks food through the intermittent microwave heating of the interior of an oven while the air being blown thereinto until the output level of a finishing sensor, which detects steam and the like developed from the food during microwave heating, reaches a set finishing level. In the electronic range, in which cooking is performed as mentioned above, the air blown into the oven is stopped over the period of time where no microwaves are generated. In addition, during the time when blast is stopped, the output level of the finishing sensor is compared with the finishing level and the cooking by microwave heating is brought to an end, when said comparison shows that the output level of the finishing sensor reaches the finishing level. As a result, the detection of vaporized object is performed highly accurately, resulting in realizing optimum cooking.