PURPOSE: To obtain a composition having excellent storage stability and curable in a short time under the curing condition, by compounding a specific reactive liquid rubber with an epoxy resin, an adduct of triazine derivative and isocyanuric acid.

CONSTITUTION: (A) A liquid rubber having carboxyl group or acid anhydride group in the molecular chain and produced by reacting maleic anhydride, thioglycolic acid, etc. to a liquid rubber during or immediately after the polymerization or after preparation of the rubber, is cured by compounding (B) an epoxy resin as a crosslinking agent and (C) 2,4-diamino-6-[2'-alkylimidazolyl(1')]-ethyl- S-triazine isocyanuric acid adduct of formula (R is alkyl; R' is H or alkyl) as a cure accelerator. The epoxy resin of the component B is preferably a compound having ≥2 epoxy groups, and the ratio of A:B is (99W30):(1W70). The amount of the component C is preferably 0.5W20% based on the component B.