Abstract: A coating liquid for forming on a substrate surface a hard coat film which exhibits a high refractive index, being excellent in resistance to hot water, weather resistance, scuffing resistance, attrition resistance and dye affinity, and which does not exhibit photochromism, is provided. A coating liquid for forming a hard coat film, comprises a matrix-forming component and composite metal oxide particles of 1 to 100 nm average particle size, composed either of an iron oxide component and a titanium oxide component used at a specified ratio or an iron oxide component, a titanium oxide component and a silica component used at a specified ratio. A substrate coated with a hard coat film is formed by applying the above coating liquid to the substrate surface and effecting drying.