A resin composition comprising the following components: a resin mixture (a) containing a component (a-1) and a component (a-2) in a total amount of the components (a-1) and (a-2) of more than 50 mass% and less than 94 mass%, the component (a-1) being a polyphenylene ether resin (a-1) and the component (a-2) being atactic homopolystyrene (a-2); a hydrogenated block copolymer (b) in an amount of 1 mass% or more and 20 mass% or less, the hydrogenated block copolymer (b) being obtained by hydrogenating at least part of a block copolymer containing a polymer block A composed mainly of a vinyl aromatic compound and a polymer block B composed mainly of a conjugated diene compound; a functional group-containing compound (c) in an amount of 0.01 mass% or more and 0.5 mass% or less, the functional group-containing compound (c) having at least one functional group selected from the group consisting of a carboxyl group and a group derived from a carboxyl group; and a surface-treated inorganic filler (d) in an amount of 5 mass% or more and less than 30 mass%, wherein the resin composition contains a polymer having a hydrogenation ratio of less than 98 % in a conjugated diene compound portion in a content of no more than 0.3 mass% per 100 mass% of the resin composition, the component (a-1) has a weight average molecular weight, Mw, determined by a method using gel permeation chromatograph using chloroform as the mobile phase and polystyrene as a reference material, of less than 70,000, and the component (b) has a number average molecular weight, Mn, determined by a method using gel permeation chromatograph using chloroform as the mobile phase and polystyrene as a reference material, of 150,000 or more and 300,000 or less. a resin mixture (a) containing a component (a-1) and a component (a-2) in a total amount of the components (a-1) and (a-2) of more than 50 mass% and less than 94 mass%, the component (a-1) being a polyphenylene ether resin (a-1) and the component (a-2) being atactic homopolystyrene (a-2); a hydrogenated block copolymer (b) in an amount of 1 mass% or more and 20 mass% or less, the hydrogenated block copolymer (b) being obtained by hydrogenating at least part of a block copolymer containing a polymer block A composed mainly of a vinyl aromatic compound and a polymer block B composed mainly of a conjugated diene compound; a functional group-containing compound (c) in an amount of 0.01 mass% or more and 0.5 mass% or less, the functional group-containing compound (c) having at least one functional group selected from the group consisting of a carboxyl group and a group derived from a carboxyl group; and a surface-treated inorganic filler (d) in an amount of 5 mass% or more and less than 30 mass%, wherein the resin composition contains a polymer having a hydrogenation ratio of less than 98 % in a conjugated diene compound portion in a content of no more than 0.3 mass% per 100 mass% of the resin composition, the component (a-1) has a weight average molecular weight, Mw, determined by a method using gel permeation chromatograph using chloroform as the mobile phase and polystyrene as a reference material, of less than 70,000, and the component (b) has a number average molecular weight, Mn, determined by a method using gel permeation chromatograph using chloroform as the mobile phase and polystyrene as a reference material, of 150,000 or more and 300,000 or less.