The present invention is a thermosetting resin composition comprising the following components: (A) a maleimide compound; (B) an epoxy resin having at least 2 epoxy groups in one molecule; (C) ) A copolymer resin having a structural unit derived from an aromatic vinyl compound and a structural unit derived from maleic anhydride; (D) silicon dioxide treated with an aminosilane-based coupling agent; and, (E ) Flame retardant dispersion.