PURPOSE: To prevent a dew formation at a sensor part and corrosion at the sensor part caused by vapor at the sensor part by a method wherein an air blowing guide for guiding cooling air and a temperature sensor where the sensor part oppositely faces against an air blowing port of the air blowing guide are arranged outside the heating chamber near the discharging port.

CONSTITUTION: There are provided an air blowing guide 13 for guiding cooling air obtained from a cooling fan and a temperature sensor 7 where a sensor part 7b oppositely faces against an air blowing port 14 of an air blowing guide 13. When a high frequency wave heating is carried out, vapor produced from food is caught by the temperature sensor 7 just before it is discharged from a discharging port 3. Heat is given or received between it and the temperature sensor 7 cooled by cooling air flowed from the air blowing guide 13, resulting in that heating is controlled in response to a variation in resistance value at the temperature sensor 7. In addition, when the heater heating operation is carried out, a temperature at the side surface 1b of the heating chamber with the temperature sensor 7 and the temperature within the heating chamber is controlled. With such an arrangement as above, it is possible to prevent dew formation at the sensor part 7b and corrosion of the sensor part 7b with vapor.