The object of the present invention is to provide a silicone resin composition for encapsulating an optical semiconductor element which has strong adhesiveness to a substrate and provide an optical semiconductor element which has high reliability. The present invention provides a silicone resin composition comprising an organopolysiloxane (A) having at least two alkenyl groups per molecule, a liner organohydrogenpolysiloxane (B-1) which has hydrogen atoms each bonded to a silicon atom at the both terminals and a liner organohydrogenpolysiloxane (B-2) which has a hydrogen atom bonded to a silicon atom at one terminal and a hydroxyl or alkoxy group bonded to a silicon atom at the other terminal, a branched organohydrogenpolysiloxane (C) having at least three hydrosilyl groups per molecule, a catalytic (D), and a condensation catalyst (E). The present invention also provides an optical semiconductor device provided with a cured product thereof.