To provide a method for producing a masked isocyanate, a crosslinking agent for a compound having any active hydrogen functional group.

When producing a masked isocyanate which is obtained by reacting an isocyanate with a phenol (both having two or more functional groups) and is a crosslinking agent for a compound having any active hydrogen functional group, the reaction is conducted in a solvent in the presence of an amine as a catalyst. It is pref. that the amine is at least one king selected from a group consisting of an aliphatic tertiary amine, an aromatic tertiary amine and an imidazole, and the solvent is at least one king selected from a group consisting of an ether, an ester and a ketone.