PURPOSE: To enable to detect scorching condition on a food to be cooked correctly as a whole by a method wherein at least one of an illuminant or a receptor is pivoted with respect to a heating chamber.

CONSTITUTION: When a heater 5 is operated to effect an oven cooking or a scorching cooking, the food to be cooked is heated by the heating of the heater 5. At this time, the illuminance 10 illuminates and a motor 16 is operated. When the motor 16 is operated, a cam 15 is rotated and an arm 12 is pivoted clockwise and counterclockwise about an axis 13. Reflected light, produced at parts A, B, C of the food to be cooked, is received sequentially by the receptor 11 by the pivoting of the receptor 11, signals, corresponding to the received light volume in the level thereof, are outputted from the receptor 11 by an by and when the level of the outputted signal has arrived at a reference value, the operation of the heater 5 is stopped and the cooking is finished.