A membrane-bound [NiFe]-hydrogenase (MBH) from Hydrogenovibrio marinus allows the direct-electron-transfer (DET)-type bioelectrocatalysis for H-2 oxidation and is an O-2-tolerant promising enzyme for the construction of enzymatic H-2-O-2 biofuel cells. However, the oxidative and reversible inactivation called "anaerobic inactivation" limits the H-2 oxidation at high potentials. In order to avoid this inhibition, we have constructed an MBH-adsorbed gas-diffusion-type electrode, in which H-2 is spontaneously supplied to the electrode from the gas phase.