NOVELTY - A hydrogen generating device (900) containing container (91), optical semiconductor electrode (100) containing substrate (101), light-blocking primary conductor layer (102) and primary semiconductor photocatalyst layer (103), counter electrode (92), conducting wire (94), and liquid (93), is prepared. At least a portion of primary semiconductor photocatalyst layer and counter electrode is in contact with liquid. The substrate is formed from a resin. The primary semiconductor photocatalyst layer is irradiated using light (1000), to generate hydrogen on counter electrode.    USE - Generation of hydrogen used for fuel cell.    ADVANTAGE - The method enables generation of hydrogen without degrading the substrate.    DETAILED DESCRIPTION - A hydrogen generating device containing a container, an optical semiconductor electrode containing a substrate, a light-blocking primary conductor layer and a primary semiconductor photocatalyst layer, a counter electrode, a conducting wire electrically connecting the primary conductor layer to the counter electrode, and a liquid stored inside the container, is prepared. The primary conductor layer is sandwiched between the substrate and the primary semiconductor photocatalyst layer. At least a portion of the primary semiconductor photocatalyst layer is in contact with the liquid. At least a portion of the counter electrode is in contact with the liquid. The liquid is chosen from an aqueous electrolyte solution and water. The substrate is formed from a resin. Then, the primary semiconductor photocatalyst layer is irradiated using light, to generate hydrogen on the counter electrode. An INDEPENDENT CLAIM is included for hydrogen generating device.    DESCRIPTION OF DRAWING(S) - The drawing shows schematic view of hydrogen generating device.    Container (91)    Counter electrode (92)    Liquid (93)    Conducting wire (94)    Optical semiconductor electrode (100)    Substrate (101)    Primary conductor layer (102)    Primary semiconductor photocatalyst layer (103)    Hydrogen generating device (900)    Light (1000)