A coating agent composition of the present invention contains photocatalyst particles composed of metal oxide in which an upper end potential of a valence band is 3 V (vs SHE) or more and a lower end potential of a conduction band is 0.16 V (vs SHE) or less. Moreover, the coating agent composition contains cuprous oxide particles, metal oxide particles without photocatalytic activity, a binder resin, and an organic solvent. Then, in 100 parts by mass of a non-volatile matter content of the coating agent composition, a content of the photocatalyst particles is 1 to 80 parts by mass, a content of the cuprous oxide particles is 0.1 to 5 parts by mass, and a total content of the photocatalyst particles and the metal oxide particles is 40 to 80 parts by mass.