Method for stopping a hydrogen generator comprising: a reformer configured to include a reforming catalyst used to generate a hydrogen-containing gas by a reforming reaction between a raw material and water; a reforming temperature detector configured to detect a temperature of the reforming catalyst; a heater configured to combust at least a part of the hydrogen-containing gas to supply heat necessary for the reforming reaction to the reformer; a combustion detector configured to detect a combustion state of the heater; a raw material supplier configured to supply the raw material; a water supplier configured to supply the water; and an operation controller, the method comprising the following steps: (a) the operation controller causes the raw material to stop operating, (b) in a case where the combustion detector detects extinction of flame, the operation controller causes the water supplier to stop operating, and (c) in a case where the reforming temperature detector detects a temperature equal to or lower than a reform replacement reference temperature, the operation controller causes the raw material supplier to start operating to supply the raw material to the hydrogen generator, wherein the reform replacement reference temperature is predetermined based on a temperature at which deposition of carbon from the raw material on the reforming catalyst does not occur. a reformer configured to include a reforming catalyst used to generate a hydrogen-containing gas by a reforming reaction between a raw material and water; a reforming temperature detector configured to detect a temperature of the reforming catalyst; a heater configured to combust at least a part of the hydrogen-containing gas to supply heat necessary for the reforming reaction to the reformer; a combustion detector configured to detect a combustion state of the heater; a raw material supplier configured to supply the raw material; a water supplier configured to supply the water; and an operation controller, the method comprising the following steps: (a) the operation controller causes the raw material to stop operating, (b) in a case where the combustion detector detects extinction of flame, the operation controller causes the water supplier to stop operating, and (c) in a case where the reforming temperature detector detects a temperature equal to or lower than a reform replacement reference temperature, the operation controller causes the raw material supplier to start operating to supply the raw material to the hydrogen generator, wherein the reform replacement reference temperature is predetermined based on a temperature at which deposition of carbon from the raw material on the reforming catalyst does not occur. (a) the operation controller causes the raw material to stop operating, (b) in a case where the combustion detector detects extinction of flame, the operation controller causes the water supplier to stop operating, and (c) in a case where the reforming temperature detector detects a temperature equal to or lower than a reform replacement reference temperature, the operation controller causes the raw material supplier to start operating to supply the raw material to the hydrogen generator, wherein the reform replacement reference temperature is predetermined based on a temperature at which deposition of carbon from the raw material on the reforming catalyst does not occur.