PURPOSE: To obtain an epoxy resin composition having excellent heat resistance, moisture resistance and mechanical properties, by compounding an epoxy resin with an acid anhydride hardener composition composed of specific amounts of a specific tetrabasic acid anhydride and alicyclic dibasic acid anhydride.

CONSTITUTION: The objective composition is obtained by compounding (A) an epoxy resin (e.g. glycidyl ether epoxy resin) with (B) an acid anhydride hardener composition composed of (i) 40W90%, preferably 45W80% tetrabasic acid anhydride of formula (R1 is H or methyl; R2 is H or lower alkyl) (preferably addition product of α-methylstyrene and maleic anhydride) and (ii) 10W60%, preferably 20W55% alicyclic dibasic acid anhydride (e.g. tetrahydrophthalic acid anhydride). The number of the acid anhydride group is preferably 0.6W1.2 per one epoxy group.

USE: For encapsulation of semiconductor, powder coating, etc.