A silicone resin is obtained by allowing a cage octasilsesquioxane having a group represented by formula (1) below, to react with an alkenyl group-containing polysiloxane containing an alkenyl group having a molarity smaller than the molarity of the hydrosilyl group of the cage octasilsesquioxane in the presence of a hydrosilylation catalyst: (where R1 represents a monovalent hydrocarbon group, R2 represents hydrogen or a monovalent hydrocarbon group, and the molar ratio of monovalent hydrocarbon group: hydrogen in R2 in the cage octasilsesquioxane as a whole is, as an average value, in a range of 6.5:1.5 to 5.5:2.5).