A hydrogen generation device (100) of the present invention includes: a transparent substrate (1); a photocatalytic electrode (4) formed of a transparent conductive layer (2) and a photocatalytic layer (3) disposed on the transparent substrate (1); a counter electrode (8) connected electrically to the transparent conductive layer (2); a water-containing electrolyte solution layer provided between the photocatalytic electrode (3) and the counter electrode (8); a separator (6) that separates the electrolyte solution layer into a first electrolyte solution layer (5) in contact with the photocatalytic electrode (4) and a second electrolyte solution layer (7) in contact with the counter electrode (8); a first gas outlet (14) for discharging a gas generated in the first electrolyte solution layer (5); and a second gas outlet (15) for discharging a gas generated in the second electrolyte solution layer (7). The photocatalytic electrode (4) and the counter electrode (8) are arranged so that a surface of the photocatalytic layer (3) and a surface of the counter electrode (8) face each other. The separator (6) allows an electrolyte in the electrolyte solution layer to pass therethrough and prevents hydrogen gas and oxygen gas in the electrolyte solution layer from passing therethrough.