A curable organopolysiloxane composition comprising: (A) a branched-chain organopolysiloxane that contains in one molecule at least three alkenyl groups and at least 30 mole % of all silicon-bonded organic groups in the form of aryl groups; (B) a linear-chain organopolysiloxane that contains aryl groups and has both molecular terminals capped with diorganohydrogensiloxy groups; (C) a branched-chain organopolysiloxane that contains in one molecule at least three diorganohydrogensiloxy groups and at least 15 mole % of all silicon-bonded organic groups in the form of aryl groups; and (D) a hydrosilylation catalyst. The composition is capable of forming a cured body that has a high index of refraction and strong adhesion to substrates.