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 (b.sub.1) to (b.sub.4): (b.sub.1) a polyvalent carboxylic acid, (b.sub.2) a polyvalent carboxylic anhydride, (b.sub.3) a reaction product of a polyvalent carboxylic acid with a compound of the following general formula (B-1), and (b.sub.4) a reaction product of a polyvalent carboxylic anhydride with a compound of the following general formula (B-2) ##STR00001## wherein R.sup.1 to R.sup.6 represent each independently a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, R.sup.3 and R.sup.4 may be bonded to form an alkylene group having 1 to 8 carbon atoms; R.sup.7 represents an alkylene group; a methylene group contained the alkylene group and the alkyl group represented by R.sup.1 to R.sup.7 may be substituted by an ether group and/or carbonyl group; Y.sup.1 and Y.sup.2 represent each independently an oxygen atom, or sulfur atom, is provided.