A hydrogen engine system for driving an engine with hydrogen gases as a fuel comprises a hydrogenated liquid fuel tank, which holds a hydrogenated liquid fuel in a liquid phase, a preheater, to which the hydrogenated liquid fuel and a dehydrogenated fuel from the hydrogen feed unit are transported and which preheats the hydrogenated liquid fuel owing to heat exchange, an vaporizer, to which the hydrogenated liquid fuel as preheated and exhaust gases of the engine are transported and which heats the hydrogenated liquid fuel to put the same in a vapor phase, and a hydrogen feed unit, to which the hydrogenated liquid fuel as vaporized and exhaust gases of the engine are transported and which generates hydrogen gases owing to dehydrogenation to transport the same to the engine.