PURPOSE: To enable the thawing of a frozen food in a short time at a low cost without causing the deterioration of the quality of the food, by irradiating the frozen food with infrared radiation and carrying out the thawing by the heat generated in the frozen food.

CONSTITUTION: An infrared radiation source A generating infrared radiation of ≥1μ wavelength (e.g. a black light source utilizing a titanium ceramic) is placed in the thawing chamber E. A frozen food (c) is placed on the table C and irradiated with infrared radiation from the infrared radiation source A through the filter B to effect the thawing of the food (c) by the temperature rise caused by the infrared radiation and the heat generated in the frozen food by the vibrational and rotational motions of the atomic structure of the food induced by the absorption of the infrared radiation in the food. After thawing, the filter B is removed, the temperature in the chamber is set to about 30W36°C to effect the fermentation of the food and the electric heater D is energized to keep the temperature in the chamber to about 150°C. The thawing, fermentation and baking of the food can be continuously carried out by this process.