A hydrogen generator is described, which comprises: a material supply device (4); a water supply device (5); an evaporator (10); a reforming catalyst layer (1) for generating reformed gas; a CO removing catalyst layer (2) configured to reduce the amount of carbon monoxide contained in the reformed gas generated by the reforming catalyst layer (1); a combustor (3) for heating the reforming catalyst layer (1) and the CO removing catalyst layer (2); a reforming temperature detector (9) for detecting the temperature of the reforming catalyst layer (1); a heater (7) for heating the CO removing catalyst layer (2); a CO removing temperature detector (8) for detecting the temperature of the CO removing catalyst layer (2); and a controller (16) configured to perform control such that the heater (7) heats the CO removing catalyst layer at the time of start-up and such that if the temperature detected by the CO removing temperature detector (8) becomes greater than or equal to a first specified value, the combustor (3) heats the reforming catalyst layer (1) and the CO removing catalyst layer (2), and if the temperature detected by the reforming temperature detector (9) becomes greater than or equal to a second specified value, the water supply device (5) starts supplying of water.