A photosemiconductor encapsulating resin composition, excellent in light transmittance, ultraviolet resistance and heat resistance, comprising the following component (A) and component (B): (A): a (meth)acrylic polymer containing an epoxy group, and (B): at least one hardener selected from the group consisting of the following components (b1) to (b4) (b1) a polyvalent carboxylic acid, (b2) a polyvalent carboxylic anhydride, (b3) a reaction product of a polyvalent carboxylic acid with a compound of the following general formula (B-1), and (b4) a reaction product of a polyvalent carboxylic anhydride with a compound of the following general formula (B-2) wherein R1 to R6 represent each independently a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, R3 and R4 may be bonded to form an alkylene group having 1 to 8 carbon atoms; R7 represents an alkylene group; a methylene group contained the alkylene group and the alkyl group represented by R1 to R7 may be substituted by an ether group and/or carbonyl group; Y1 and Y2 represent each independently an oxygen atom, or sulfur atom, is provided.