PURPOSE: To obtain a urethane curing agent useful as a raw material for automobile parts, furniture, sporting goods, building materials, clothes, coating materials, etc., having excellent weather resistance and heat resistance by using both a diisocyanate compound and a polyisocyanate compound.

CONSTITUTION: An aliphatic and/or alicyclic diisocyanate compound is blended with a polyisocyanate compound containing isocyanurate bond shown by formula I, uretdione bond shown by formula II or carbodiimide bond at room temperature and a mixed crude solution is used as it is, as a urethane curing agent. Or in order to correspond various uses, the unreacted diisocyanate compound is once removed, the polyisocyanate is left alone once and dissolved in the diisocyanate compound to give the aimed substance. 5-80wt.% polyisocyanate compound exists in the urethane curing agent.