Abstract: A method for producing a photocatalytic, which can produce a photocatalyst showing high photocatalytic activity, is provided. The present invention relates to a method for producing noble metal-supported photocatalyst particles wherein a noble metal is supported on the surface of the photocatalyst particles, and a method for producing a dispersion of the noble metal-supported photocatalyst particles, the methods comprising steps of: blowing an inert gas into a raw dispersion in which the photocatalyst particles are dispersed and a precursor of the noble metal is dissolved in a dispersion medium; and irradiating the raw dispersion with light having energy larger than that of a bandgap of the photocatalyst particles, thereby supporting the noble metal on the surface of the photocatalyst particles.