The present invention provides a hydrogen generation device using a photocatalyst to generate hydrogen from liquid water or water vapor and a method of using the same. The hydrogen generation device of the present invention has a water channel through which liquid water or water vapor flows, and which has an outer circumferential wall made at least in part of a transparent material; a hydrogen channel through which hydrogen flows and which is located at the inner circumference side of the water channel; a hydrogen separating membrane forming at least part of a wall between the water channel and hydrogen channel, separating hydrogen from the liquid water or water vapor in the water channel, and providing the hydrogen to the hydrogen channel; and a photocatalyst layer arranged on least at part of the water channel-side surface of the hydrogen separating membrane.