β-ZrNCl has attracted attention because of its superconductivity and high photothermal conversion efficiency in atomic thickness. Although the positions of the valence band maximum (VBM) and the conduction band minimum (CBM) have not been experimentally obtained, the bandgap (2.6 eV) has already been confirmed to absorb visible light. Density functional theory (DFT) calculations also show that the electron mobility of singlelayer ZrNCl is very high and the carrier density is relatively low. These physical properties indicate that β-ZrNCl can be a candidate material as a new mixed anion photocatalyst (N−Cl system). Here, we investigated the band structure of β-ZrNCl and the photocatalytic activity for water splitting. The CBM and VBM were estimated to be −0.84 and +1.69 V (vs NHE), respectively. H 2 and O 2 were evolved in the presence of sacrificial hole and electron scavengers under visible-light irradiation (λ = 450 nm). These results indicate that the β-ZrNCl system functions as a visible-light-driven photocatalyst capable of water splitting.