A heating device of a food material that can heat a food material while preventing oxidation reaction and the like of the food material as much as possible is provided. A food material 8 is held under a reductive atmosphere where air is eliminated by filling superheated steam in a heating chamber 10 at a pressure exceeding an atmospheric pressure. Thus, because the food material 8 is heated under the reductive atmosphere where air is eliminated by filling the superheated steam, not under a conventional atmosphere where oxygen and nitrogen exist. Therefore, a Maillard reaction and an oxidation reaction can be suppressed, and a thermochemical reaction which could not be caused in the conventional heating method is caused in the food material 8. Thereby, it can be expected that the heated food material 8 acquires a characteristic which did not exist in the past, with less degradation.