A photoelectrode (100) of the present invention includes a conductive layer (12) and a photocatalytic layer (13) provided on the conductive layer (12). The conductive layer (12) is made of a metal nitride. The photocatalytic layer (13) is made of at least one selected from the group consisting of a nitride semiconductor and an oxynitride semiconductor. When the photocatalytic layer (13) is made of a n-type semiconductor, the energy difference between the vacuum level and the Fermi level of the conductive layer (12) is smaller than the energy difference between the vacuum level and the Fermi level of the photocatalytic layer (13). When the photocatalytic layer (13) is made of a p-type semiconductor, the energy difference between the vacuum level and the Fermi level of the conductive layer (12) is larger than the energy difference between the vacuum level and the Fermi level of the photocatalytic layer (13).