PURPOSE: To simplify the structure of a sensor in the automatic oven, to simplify the control by the sensor and to exactly perform the cooking according to the menu.

CONSTITUTION: A turn table 2 for placing the food 3 to be cooked thereon is provided on the lower part in an oven chamber 1, and a magnetron high-frequency oscillator 4, an oven and a heater 5 are provided on the upper part therein. A speaker 6 for applying the pressure of the chamber and a microphone 7 for detecting the pressure change in the chamber are provided on an oven wall surface. And a normal chamber 8 whose content volume is fixed is provided on the oven wall, and a speaker 9 and a microphone 10 are provided thereon. The pressure is respectively applied to the oven chamber 1 and the normal chamber 8 by driving speakers 6, 9, then the pressure in the room, changing on the based of the law of gaseous reaction is detected by the microphones 7, 9. The cooking state signal is obtained from the volume change of the food 3 in the oven chamber 1 by computing the ratio between both detecting signals by means of a devider 16. And then, the obtained signal is fed to a CPU 18 to perform the cooking control according to the menu.