A method of operating a hydrogen generating apparatus, said hydrogen generating apparatus comprising: a reformer configured to generate a hydrogen-containing gas from a material gas through a reforming reaction; a material gas feeding passage through which the material gas is fed to the reformer; a material gas feeding device which is provided on the material gas feeding passage and is configured to control feeding of the material gas to the reformer; a combustor configured to combust a gas discharged from the reformer; an ignition device provided in the combustor; a combustible gas feeding passage through which the gas discharged from the reformer is fed to the combustor; and a valve provided in the combustible gas feeding passage; and a controller configured to, during a stop period, perform a maintaining process in such a manner that the material gas feeding device is controlled to feed the material gas to a gas passage which is located between the material gas feeding device and the valve, to maintain a pressure in an interior of the gas passage at a value which is not smaller than a first threshold which is an atmospheric pressure or larger; and wherein when the controller detects there is an abnormality in the maintaining process, the controller controls the material gas feeding device and the ignition device to feed the material gas to the gas passage with an amount which is larger than an amount in a case where the controller detects there is no abnormality in the maintaining process, during a period which lapses from when the controller detects the abnormality until the ignition device starts an ignition operation in a start-up process. a reformer configured to generate a hydrogen-containing gas from a material gas through a reforming reaction; a material gas feeding passage through which the material gas is fed to the reformer; a material gas feeding device which is provided on the material gas feeding passage and is configured to control feeding of the material gas to the reformer; a combustor configured to combust a gas discharged from the reformer; an ignition device provided in the combustor; a combustible gas feeding passage through which the gas discharged from the reformer is fed to the combustor; and a valve provided in the combustible gas feeding passage; and a controller configured to, during a stop period, perform a maintaining process in such a manner that the material gas feeding device is controlled to feed the material gas to a gas passage which is located between the material gas feeding device and the valve, to maintain a pressure in an interior of the gas passage at a value which is not smaller than a first threshold which is an atmospheric pressure or larger; and wherein when the controller detects there is an abnormality in the maintaining process, the controller controls the material gas feeding device and the ignition device to feed the material gas to the gas passage with an amount which is larger than an amount in a case where the controller detects there is no abnormality in the maintaining process, during a period which lapses from when the controller detects the abnormality until the ignition device starts an ignition operation in a start-up process.