A hydrogen generating system comprising: a plurality of hydrogen generating devices connected in parallel; and a controller, wherein each of the plurality of hydrogen generating devices includes a reformer that generates a hydrogen-containing gas from a raw material, a carbon monoxide remover that decreases a concentration of carbon monoxide contained in the hydrogen-containing gas by using a selective oxidation catalyst and an oxidizing gas, an oxidizing gas feeder that supplies the oxidizing gas to the CO remover, a raw material supply passage through which the raw material is supplied to the reformer, a raw material supply unit provided in a middle of the raw material supply passage, a hydrogen supply passage through which the hydrogen-containing gas discharged from the CO remover is supplied to a hydrogen utilization device, a recycle passage that is branched at a branching point from a middle of the hydrogen supply passage to mix at least part of the hydrogen-containing gas discharged from the CO remover into the raw material, and a hydrogen supply passage sealing valve provided downstream of the branching point in the hydrogen supply passage, the controller is configured to cause at least one of the plurality of hydrogen generating devices to perform a second action to supply the oxidizing gas and the hydrogen-containing gas to the CO remover, while at least another of the plurality of hydrogen generating devices performs a first action to supply the hydrogen-containing gas to the CO remover with the supply of the oxidizing gas to the CO remover stopped, and the controller is configured to close the hydrogen supply passage sealing valve of the at least another of the plurality of hydrogen generating devices that currently performs the first action to mix the hydrogen-containing gas discharged from the CO remover of the at least another of the plurality of hydrogen generating devices that currently performs the first action into the raw material through the recycle passage. a plurality of hydrogen generating devices connected in parallel; and a controller, wherein each of the plurality of hydrogen generating devices includes a reformer that generates a hydrogen-containing gas from a raw material, a carbon monoxide remover that decreases a concentration of carbon monoxide contained in the hydrogen-containing gas by using a selective oxidation catalyst and an oxidizing gas, an oxidizing gas feeder that supplies the oxidizing gas to the CO remover, a raw material supply passage through which the raw material is supplied to the reformer, a raw material supply unit provided in a middle of the raw material supply passage, a hydrogen supply passage through which the hydrogen-containing gas discharged from the CO remover is supplied to a hydrogen utilization device, a recycle passage that is branched at a branching point from a middle of the hydrogen supply passage to mix at least part of the hydrogen-containing gas discharged from the CO remover into the raw material, and a hydrogen supply passage sealing valve provided downstream of the branching point in the hydrogen supply passage, a reformer that generates a hydrogen-containing gas from a raw material, a carbon monoxide remover that decreases a concentration of carbon monoxide contained in the hydrogen-containing gas by using a selective oxidation catalyst and an oxidizing gas, an oxidizing gas feeder that supplies the oxidizing gas to the CO remover, a raw material supply passage through which the raw material is supplied to the reformer, a raw material supply unit provided in a middle of the raw material supply passage, a hydrogen supply passage through which the hydrogen-containing gas discharged from the CO remover is supplied to a hydrogen utilization device, a recycle passage that is branched at a branching point from a middle of the hydrogen supply passage to mix at least part of the hydrogen-containing gas discharged from the CO remover into the raw material, and a hydrogen supply passage sealing valve provided downstream of the branching point in the hydrogen supply passage, the controller is configured to cause at least one of the plurality of hydrogen generating devices to perform a second action to supply the oxidizing gas and the hydrogen-containing gas to the CO remover, while at least another of the plurality of hydrogen generating devices performs a first action to supply the hydrogen-containing gas to the CO remover with the supply of the oxidizing gas to the CO remover stopped, and the controller is configured to close the hydrogen supply passage sealing valve of the at least another of the plurality of hydrogen generating devices that currently performs the first action to mix the hydrogen-containing gas discharged from the CO remover of the at least another of the plurality of hydrogen generating devices that currently performs the first action into the raw material through the recycle passage.