Disclosed is a hydrogen generator which comprises a reformer (20) containing a reforming catalyst for generating a hydrogen-containing gas through the reforming reaction between a raw material and water, a reforming temperature detection unit (18) for detecting the temperature of a reforming catalyst, a heating unit (2) for burning at least a part of the hydrogen-containing gas to supply heat in a required amount for the reforming reaction to the reformer (20), a combustion detection unit (22) for detecting the burning state in the heating unit (2), a raw material supply unit (4) for supplying a raw material, a water supply unit (3) for supplying water, and an operation control unit (16). The operation control unit (16) can stop the operation of the raw material supply unit (4) when the operation of the hydrogen generator is stopped, can stop the operation of the water supply unit (3) when the quenching of flame is detected in the combustion detection unit (22), and can bring the raw material supply unit (4) into operation so that the raw material is supplied to the hydrogen generator when a temperature equal to or lower than the reference temperature for the reformation/replacement is detected in the reforming temperature detection unit (18).