A soundproof panel comprising a nonwoven structural member and a board member is prepared. A paste containing at least a carbon powder having a catalyst supported thereon is spread over a predetermined support, and the coated support is dried to form the catalyst layer. Hollow portions are provided in a formation region of the light-shielding layers, each hollow portion being shaped so that a cross-sectional area obtained by cutting along a plane parallel to the one surface of the base material is large on the light-shielding layer side and is gradually decreased as being away from the light-shielding layer.