To provide a method of producing a millable urethane rubber excellent in moldability and having good mechanical properties.

The method of producing the millable urethan rubber comprises preparing a millable urethane resin (A) by reacting and hardening a liquid mixture of a polyol constituent (a) containing a polyol having at least one ethylenic unsaturated group in the molecular side chain and an isocyanate constituent (b) on the surface of or in the bag of a thermoplastic resin film (B) having a melting point of 60-110C, adding a curing agent thereto, and melting and kneading without removing the (B), to harden the resultant mixture.