A hydrogen generator of the present invention includes: a raw material supplying device (4) configured to supply a raw material; a water supplying device (3) configured to supply water; an evaporator (23) configured to evaporate the water supplied from the water supplying device (3) to generate steam; a reformer (20) having a reforming catalyst which generates a hydrogen-containing gas by a reforming reaction using the raw material and the steam; a valve (12) disposed on a gas passage to cause the reformer (20) to be communicated with an atmosphere and block the reformer (20) from the atmosphere, the gas passage being located downstream of the reformer (20); and a controller (11) configured to stop supplying the water from the water supplying device (3), then continue to supply the raw material from the raw material supplying device (4) with the valve (12) open, and stop supplying the raw material from the raw material supplying device (4) and close the valve (12) before an inside of the reformer (20) is purged with the raw material.