PURPOSE: To ensure that self-cleaning catalyst vitreous enamel brings its self-cleaning performance into full play and a cooking chamber is always kept clean, by causing a hot blast blown off by a fan to impinge upon the inside wall of the cooking chamber while being held at a maximum temperature.

CONSTITUTION: As air blown by a fan 9 is heated by a heater 10 and then caused to directly flow along the inside wall of a cooking chamber 5, the inside wall is heated to a high temperature (e.g. 250°C), self-cleaning catalyst vitreous enamel brings its self-cleaning performance into full play, and the inside wall is always kept clean. Although the temperature of the hot blast impinging on a cooked body is slightly lower than that of the hot blast impinging on the inside wall, it does not interfere with cooking in any way. In another embodiment, a hot blast may be fed from the outside to a fan chamber by using as a heat source a gas or the like instead of the heater 10 and may be blown off into the cooking chamber 5 by the fan 9.