A silicone resin composition contains a cage octasilsesquioxane having a group represented by the following formula (1), an alkenyl group-containing polysiloxane containing an alkenyl group having a number of moles larger than that of a hydrosilyl group in the cage octasilsesquioxane, a hydrosilylation catalyst, and an organohydrogenpolysiloxane. (where, in formula, R1 represents a monovalent hydrocarbon group selected from a saturated hydrocarbon group and an aromatic hydrocarbon group. R2 represents hydrogen or a monovalent hydrocarbon group selected from a saturated hydrocarbon group and an aromatic hydrocarbon group. The molar ratio of the monovalent hydrocarbon group:hydrogen in R2 in the cage octasilsesquioxane as a whole is, as an average value, in the range of 6.5:1.5 to 5.5:2.5).