PURPOSE: To improve the storage stability and curability of titled composition thereby to prevent the degradation of the characteristics, by employing a specified imidazole compound as a cure accelerator and an alkylarylsilsesquioxane type silicone compound as a modifying agent.

CONSTITUTION: This resin composition comprises an epoxy resin, curing agent, a cure accelerator and a modifying agent. Said cure accerelator is at least one imidazole compound selected from the group consisting of 2-undecylimidazole, 2-heptadecylimidazole, 1-cyanoethyl-2-undecylimidazole and 2,4-diamino-6-[2'- undecylimidazolyl-(1')]-ethyl-s-triazine. And said modifying agent is an alkylarylsilsesquioxane type silicone compound represented by the formula, wherein R1WR6 are each a C6W9 aryl or a C1W4 alkyl. This composition has excellent storage stability and curability, and shows less deterioration in volume specific resistance at high temperature and high humidity. Accordingly, this composition is useful as a sealing resin for electronic circuit parts.