To provide a method and an apparatus for efficiently producing hydrogen with a specific microorganism, in further detail, the method and the apparatus for producing the hydrogen by which even insoluble starches can simultaneously be solubilized during culture to efficiently produce the hydrogen with advantages to thermal energy since a high temperature (e.g. 300°C) is not required and contamination with other microorganisms is avoided since the hydrogen can be produced at about 85°C optimum temperature without relating to various disadvantages accompanying light irradiation such as sticking of organic substances, et., to irradiating parts due to no need of the light irradiation and without causing problems such as corrosion or environmental pollution since hydrogen sulfide is scarcely emitted.

The microorganism of the genus Thermococcus, especially Thermococcus kodakaraensis KOD1 is cultured by using a culture fluid containing pyruvic acid or its salt or/and starchy polysaccharides added thereto. Thereby, the hydrogen is produced in microbial cells.