A polyphenylene ether resin composition includes (A) a modified polyphenylene ether that is end-modified with a substituent having a carbon-carbon unsaturated double bond, and (B) a crosslinking agent having a carbon-carbon unsaturated double bond. The crosslinking agent serving as component (B) includes from 50 to 100 mass % of (B-1) divinylbenzene and (B-2) polybutadiene. Components (A) and (B) are included in a ratio therebetween, expressed as the mass ratio (A):(B), of from 65:35 to 95:5. Components (B-1) and (B-2) are included in a ratio therebetween, expressed as the mass ratio (B-1):(B-2), of from 1:100 to 1.5:1.