One aspect of the present invention relates to a resin composition comprising: a modified polyphenylene ether compound whose end is modified by a substituent having a carbon-carbon unsaturated double bond; a cross-linking curing agent having a carbon-carbon an unsaturated double bond; a silane coupling agent having a phenylamino group in the molecule; and silicon dioxide, wherein the The content of the silicon dioxide is 60-250 parts by mass.