A two-part curing high-durable polyurethane elastomer composition having excellent heat resistance and wet heat resistance, and excellent workability such that a viscosity after two-part mixing is suitable for casting workability which comprises (i) a polyisocyanate component, and (ii) an active hydrogen-containing compound comprising (A) a polyol having a hydroxyl value of from 25 to 55 obtained by reacting a castor oil fatty acid, 12-hydroxystearic acid, or a condensate of their fatty acids, with a polyol (X) having a molecular weight of from 400 to 1,500, and (B) a polyol having a hydroxyl value of from 100 to 500 obtained by ring opening an epoxidized fatty acid ester with a polyhydric alcohol.