The present invention is a curable organopolysiloxane composition containing (A) a compound shown by the following average composition formula (1), wherein R1 represents an aliphatic unsaturated group, R2 represents a monovalent hydrocarbon group, R3 represents an aliphatic hydrocarbon group, Ar represents an aryl group, and “n” and “m” represent positive numbers which satisfy n≧1, m≧1, and n+m≧10, (B) a hydrogen atom-containing organic silicon compound having at least two silicon atom-bonded hydrogen atoms per one molecule while not having an aliphatic unsaturated group, and (C) a hydrosilylation catalyst which contains a platinum group metal. Thereby, there can be provided a curable organopolysiloxane composition which can give a cured product having high transparency, high refractive index, and excellent thermal shock resistance; an optical device sealing material; and an optical device.