PURPOSE: To improve the moisture resistance and rust prevention of an epoxy resin, by adding a specified silicone compound and oxidized carnauba wax to the epoxy resin.

CONSTITUTION: A curing agent, an alkylarylsilsesquioxane silicone compound of the formula (wherein 1W6R are earch an alkyl or the like) and an additive comprising oxidized carnauba wax are added to an epoxy resin. Said silicone compound is added to the epoxy resin in an amount of, preferably, 0.1W5pts.wt. per 100pts.wt. epoxy resin. The resulting epoxy resin composition is throught to be effective in improving moisture resistance and rust prevention in such a way that when the composition is used as a sealing resin or the like, the above additive is sandwiched between the composition and an adherend and preventes external moisture and ionic impurities from penetrating into the surface of the adherend.