Provided are resin compositions which satisfactorily infiltrate into base materials and with which it is possible to produce a prepreg, a metal-clad laminate, and a printed wiring board that have excellent properties such as low warpage, flame retardancy, low thermal expansion, drillability, and resistance to desmear. Also provided are a resin sheet produced using one of the resin compositions, a prepreg produced using one of the resin compositions, a metal-clad laminate produced using one of the resin compositions or the prepreg, a printed wiring board produced using at least one of the metal-clad laminate, the prepreg, and the resin compositions, and a semiconductor device having excellent performance produced using the printed wiring board. The first of the resin compositions comprises an epoxy resin, a first inorganic filler of an indefinite shape, and a second inorganic filler which differs in average particle diameter from the first inorganic filler and in which the average particle diameter is 10-100 nm. The second of the resin compositions comprises an epoxy resin, fine silicone rubber particles having an average particle diameter of 1-10 [mu]m, fine boehmite particles having an average particle diameter of 0.2-5 [mu]m, and silica nanoparticles having an average particle diameter of 10-100 nm.