NOVELTY - Producing a catalyst layer (15)-supporting substrate, comprises: forming a laminated body on a substrate by alternately forming first layers and second layers, where the forming step further comprises forming the first layers by sputtering or vapor deposition with a catalyst material, and forming the second layers by sputtering or vapor deposition with a pore-forming material, an average thickness of which per second layer being 10-500 nm; and forming pores by removing the pore-forming material in the second layers by solubilization.    USE - The method is useful for producing a catalyst layer-supporting substrate, which is useful in fuel cell (claimed).    ADVANTAGE - The method ensures economical production of catalyst layer-supporting substrate with less consumption of noble metal catalyst material and high quality thus enabling high performance of fuel cell.    DETAILED DESCRIPTION - Producing a catalyst layer (15)-supporting substrate, comprises: forming a laminated body on a substrate (1) by alternately forming first layers (12) and second layers (13), where the forming step further comprises forming the first layers by sputtering or vapor deposition with a catalyst material, a content of the catalyst material of which per first layer being equivalent to a content of a flat layer with a thickness of 0.3-4 nm which consist of the catalyst material solely and forming the second layers by sputtering or vapor deposition with a pore-forming material, an average thickness of which per second layer being 10-500 nm; and forming pores by removing the pore-forming material in the second layers by solubilization. INDEPENDENT CLAIMS are included for:    (1) a catalyst layer-supporting substrate comprising a substrate, and catalyst layer formed on the substrate, where the catalyst layer comprises a catalyst material and pores, the catalyst material has a layer or wire shape, a half-value width of a main peak of the catalyst material, as determined from X-ray diffraction spectrum of the catalyst layer, is 1.5 degrees or more; and a porosity of the catalyst layer is 30% or more; and    (2) a fuel cell comprising an anode catalyst layer, a cathode catalyst layer and a proton-conductive membrane provided between the anode catalyst layer and the cathode catalyst layer, where one of the anode catalyst layer and the cathode catalyst layer is a catalyst layer of the catalyst layer supporting substrate.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic cross-sectional view illustrating a step of producing the catalyst-supporting substrate.    Substrate (1)    First layer (12)    Second layer (13)    Catalyst layer. (15)