A curable polyorganosiloxane composition for use in an LED or optical lens, including: (A) an alkenyl group-containing polyorganosiloxane which contains a (A1) branched polyorganosiloxane including an SiO4/2 unit and an R3SiO1/2 unit, and optionally an R2SiO unit and/or an RSiO3/2 unit, wherein at least three R per molecule are vinyl groups, and optionally (A2) a linear polyorganosiloxane having R bonded to a silicon atom, wherein at least two R per molecule are vinyl groups, wherein 100 mol % or more of the R present in components (A1) and (A2), excluding alkenyl groups, are methyl groups; (B) a polyalkylhydrogensiloxane including an SiO4/2 unit and an R3(CH3)2SiO1/2 unit, the polyalkylhydrogensiloxane having the formula [R3(CH3)2SiO1/2]8[SiO4/2]4 or [R3(CH3)2SiO1/2]10[SiO4/2]5, wherein each R3 represents a hydrogen atom, and (C) a platinum-vinylsiloxane complex. The composition having desirable light transmission properties, and is unlikely to suffer yellowing due to exposure to heat.