PURPOSE: To obtain a curable coating agent exhibiting excellent adhesiveness to the surface of a base material consisting of a hydrophobic resin by incorporating a specified org. compd. and an org. polyisocyanate as main ingredients.

CONSTITUTION: The title coating agent is a curable coating agent consisting of an org. compd. of formula I with a number average mol.wt. of 300-20,000 and an org. polyisocyanate. In the formula I, A is a group of formula II; B is -R3O-; a bond between A and B is of random or block type; Z is a residue of an active hydrogen compd.; R1 is a 1-10C alkylene; R2 is a 1-20C alkyl, alkenyl, aryl or alkylaryl; R3 is a 4C or higher alkylene; a is 0-100; k is 1-12; m is 1-250; and n is 0-5. As the org. compd. of formula I, a compd. obtd. by reacting an active hydrogen compd. with a glycidyl ether in the presence of a catalyst so as to have a mol.wt. of 300-20,000, namely a value of m in the formula I of 1-250 can be cited.