Abstract Photocatalytic degradation of volatile organic compounds under visible light is an important issue for use of solar energy. Perovskite-type oxide, KLaTi2O6, was prepared by the sol-gel method. Photocatalytic activities of catalysts for chlorobenzene decomposition were investigated. Four types of transition metal (Co, Ni, Zn, Mn) were doped into KLaTi2O6 to improve photocatalytic activity for gas-phase chlorobenzene degradation. Photocatalysts were characterized by X-ray diffraction, energy-dispersive X-ray spectroscopy, ultraviolet–visible spectroscopy, and nitrogen adsorption analysis. Results showed that under visible light irradiation, the photocatalytic activity of metal-doped KLaTi2O6 was higher than undoped KLaTi2O6. We found that the predominant species accumulating on the catalyst surface is benzaldehyde. This report proposes the pathway of benzaldehyde formation during photocatalytic degradation of chlorobenzene under visible light irradiation.