To prevent a coated steel plate from becoming easily rusty even when its coat is flawed by forming a photocatalytic layer on the coated surface of the coated steel plate obtained by coating a resin on the surface of a metal base material.

A resin 2 is applied on the surface of a metal base material 1 and a photocatalytic layer 3 is formed on the coated resin 2. Alternately, the resin 2 is coated on a metal base material 1, then an intermediate layer is formed on the coated resin 2, and further, a photocatalytic layer 3 is formed on the intermediate layer. As another laminating process, the resin 2 is coated on the surface of the metal base material 1, then the photocatalytic layer 3 is formed on the coated resin 2, and a protecting layer is formed on the photocatalytic layer 3. The metal base material 1 to be used is an iron plate or a stainless steel plate, and the resin 2 to be coated is acryl or urethane. The substances to be used as the photocatalyst are anatase-type titanium oxide, rutile-type titanium oxide, strontium titanate, zinc oxide, tin oxide, tungsten trioxide and bismuth sesquioxide.