A prepreg includes a resin composition including: (A) at least one of an epoxy resin having a naphthalene skeleton and a phenolic hardener having a naphthalene skeleton; (B) a polymer having at least the structures of formulae (2) and (3) among formulae (1), (2) and (3) and having a weight-average molecular weight of from 200,000 to 850,000 inclusive; and (C) an inorganic filler: wherein x:y:z (molar fraction)=0:0.95:0.05 to 0.2:0.6:0.2 (where x+y+z≦1, 0≦x≦0.2, 0.6≦y≦0.95, 0.05≦z≦0.2); R1 represents a hydrogen atom or a methyl group and R2 includes at least one of a glycidyl group and an epoxidized alkyl group among a hydrogen atom, an alkyl group, a glycidyl group and an epoxidized alkyl group in formula (2); and R3 represents a hydrogen atom or a methyl group and R4 represents Ph (phenyl group), —COOCH2Ph or —COO(CH2)2Ph in formula (3).