The disclosed method for producing hydrogen by means of thermochemical water-splitting can efficiently use solar energy obtained by means of a beam-down typed light collecting system. Further disclosed is a device for producing hydrogen. While circulating within a reactor (1) a fluidized bed (2) made of metal oxide particles, two reactions are simultaneously caused to proceed: a thermal reduction reaction, which is an oxygen evolution reaction wherein a portion of the fluidized bed (2) is heated by solar light (S) in a nitrogen atmosphere, which is a low oxygen partial pressure gas, releasing oxygen from the metal oxide; and a thermochemical water-splitting reaction, which is a hydrogen evolution reaction wherein water vapor is brought into contact with the metal oxide after oxygen has been released, generating hydrogen.