PROBLEM TO BE SOLVED: To inexpensively provide a photocatalyst that can be utilized for organic matter decomposition or sterilization and has high safety without being limited by utilization scenes.SOLUTION: The photocatalyst comprises as an active component a divalent iron ion or a trivalent iron ion. Specifically, the photocatalyst exhibits organic matter decomposition activity upon irradiating with light having a wavelength which belongs to ultraviolet light. A method for decomposing organic matter comprises contacting the photocatalyst with an object to be decomposed and irradiating with light having a wavelength which belongs to ultraviolet light. A sterilization method comprises contacting the photocatalyst with an object to be sterilized and irradiating with light having a wavelength which belongs to ultraviolet light.
