A curable silicone composition comprising: 100 parts by mass of mixture of component (A 1) and component (A 2) wherein component (A 1) is an organopolysiloxane having at least two alkenyl groups in a molecule, and free of silicon-bonded hydroxyl groups and silicon-bonded hydrogen atoms, and component (A 2) a branched chain organopolysiloxane represented by the following average unit formula: (R 1 2 R 2 SiO 1/2)a (R 1 3SiO 1/2) b (SiO 4/2)c (HO 1/2) d wherein R 1 are the same or different alkyl groups having from 1 to 10 carbons; R 2 is an alkenyl group; and "a", "b", "c" and "d" are all positive numbers that satisfy the following conditions: a+b+c = 1; a/(a+b) = 0.15 to 0.35; c/(a+b+c) = 0.53 to 0.62; and d/(a+b+c) = 0.005 to 0.03; an organopolysiloxane having at least two silicon-bonded hydrogen atoms in a molecule, in an amount that provides from 0.1 to 10 moles of silicon-bonded hydrogen atoms in this component per 1 mole of the alkenyl groups in component; from 0.01 to 10 parts by mass of a diorganodialkoxysilane represented by the following general formula: R 3 R 4 Si(OR 5) 2 wherein R 3 is a glycidoxyalkyl group, an epoxycyclohexylalkyl group, an epoxyalkyl group, an acryloxyalkyl group, or a methacryloxyalkyl group; R 4 is an alkyl group having from 1 to 6 carbons; and R 5 is an alkyl group having from 1 to 4 carbons; from 0.01 to 10 parts by mass of a straight chain organosiloxane oligomer having at least one silicon-bonded hydroxyl group in a molecule and free of silicon-bonded hydrogen atoms and selected from the group of a copolymer oligomer of dimethylsiloxane and methylvinylsiloxane capped at both molecular terminals with silanol groups, a methylvinylsiloxane oligomer capped at both molecular terminals with silanol groups and a dimethylsiloxane oligomer capped at both molecular terminals with silanol groups; and a catalytic amount of a hydrosilylation catalyst. 100 parts by mass of mixture of component (A 1) and component (A 2) wherein component (A 1) is an organopolysiloxane having at least two alkenyl groups in a molecule, and free of silicon-bonded hydroxyl groups and silicon-bonded hydrogen atoms, and component (A 2) a branched chain organopolysiloxane represented by the following average unit formula: (R 1 2 R 2 SiO 1/2)a (R 1 3SiO 1/2) b (SiO 4/2)c (HO 1/2) d wherein R 1 are the same or different alkyl groups having from 1 to 10 carbons; R 2 is an alkenyl group; and "a", "b", "c" and "d" are all positive numbers that satisfy the following conditions: a+b+c = 1; a/(a+b) = 0.15 to 0.35; c/(a+b+c) = 0.53 to 0.62; and d/(a+b+c) = 0.005 to 0.03; an organopolysiloxane having at least two silicon-bonded hydrogen atoms in a molecule, in an amount that provides from 0.1 to 10 moles of silicon-bonded hydrogen atoms in this component per 1 mole of the alkenyl groups in component; from 0.01 to 10 parts by mass of a diorganodialkoxysilane represented by the following general formula: R 3 R 4 Si(OR 5) 2 wherein R 3 is a glycidoxyalkyl group, an epoxycyclohexylalkyl group, an epoxyalkyl group, an acryloxyalkyl group, or a methacryloxyalkyl group; R 4 is an alkyl group having from 1 to 6 carbons; and R 5 is an alkyl group having from 1 to 4 carbons; from 0.01 to 10 parts by mass of a straight chain organosiloxane oligomer having at least one silicon-bonded hydroxyl group in a molecule and free of silicon-bonded hydrogen atoms and selected from the group of a copolymer oligomer of dimethylsiloxane and methylvinylsiloxane capped at both molecular terminals with silanol groups, a methylvinylsiloxane oligomer capped at both molecular terminals with silanol groups and a dimethylsiloxane oligomer capped at both molecular terminals with silanol groups; and a catalytic amount of a hydrosilylation catalyst.