To provide a photocatalyst coating liquid capable of forming a photocatalyst layer having excellent adhesiveness to a substrate on the substrate and exhibiting high photocatalytic activity by irradiating the photocatalyst layer with a practical light source such as a fluorescent lamp, and a product having a photocatalytic function and provided with the photocatalyst layer on the surface.

The photocatalyst coating liquid comprises (1) photocatalyst particles, (2) niobium oxide sol particles, (3) colloidal silica particles, (4) a silicon alkoxide, and (5) a solvent at a specific ratio, wherein the solid content obtained by volatilizing volatile components from the photocatalyst coating liquid has a predetermined ratio relative to the amount of photocatalyst coating liquid.