PURPOSE: To simply and efficiently remove a hydrolyzable chlorine compound in an organic isocyanate which is hardly removed according to a conventional method.

CONSTITUTION: The subject method is to purify an organic isocyanate characterized as follows. An imidazole compound in an amount of equiv. or more to chlorine in a hydrolyzable chlorine compound in the organic isocyanate containing the hydrolyzable chlorine compound is added and reacted with the chlorine compound. The resultant reaction mixture is then distilled.