A silicon-containing curable composition, comprising: a prepolymer (A) containing two or more Si—H groups per molecule obtained by hydrosilylation reaction of one kind or more selected from each of components (α) and components (β) described below; a cyclic siloxane compound (B) containing per molecule two or more carbon-carbon double bonds that have reactivity to the Si—H groups; and a hydrosilylation catalyst (C); wherein the component (α) is a cyclic siloxane compound represented by formula (1) and contains two or more Si—H groups per molecule, wherein R1, R2 and R3 each are an alkyl group having 1 to 6 carbon atoms or a phenyl group, may be the same or different, a is any number of 2 to 10, b is any number of 0 to 8, and a+b≧2, and wherein the component (β) is a compound containing per molecule two or more carbon-carbon double bonds that have reactivity to the Si—H groups.