An object of the present invention is to provide an antiviral agent which exhibits high antiviral activity even under irradiation with visible light and is capable of detoxifying a virus. The antiviral agent according to the present application is composed of a dispersion containing noble metals and photocatalyst particles as supported by the noble metals, the dispersion containing 0.01 part by mass to 1 part by mass of noble metal atoms based on 100 parts by mass of photocatalyst particles.
