The hydrogenase extracted from sulfate-reducing bacteria (Desulfovibrio vulgaris) was immobilized in a photosensitive poly(vinyl alcohol) with 7-styrylpyridinium residue by exposing to UV light for a few minutes. The immobilized hydrogenase was 92%. The efficiency of hydrogen evolution of immobilized hydrogenase, methylviologen and sodium dithionite was observed. The resistivities of the immobilized film against the inactivation of air and the thermal treatment were 35 times stronger and 20°C higher than those before immobilization.