To provide a method for producing a monoisocyanate compound useful for directly converting a natural trifunctional polyol such as castor oil or lesquerella oil to a bifunctional polyol and having high safety and obtain a composition for polyurethane having low viscosity and good workability in production of polyurethane and capable of providing a cured product excellent in hue and free from surface tackiness.

This method for producing a monoisocyanate compound comprises reacting a diisocyanate having ≤300 molecular weight with a monohydroxy compound equivalent or less to the diisocyanate and then removing excess diisocyanate by vacuum distillation. This polyurethane composition contains a reaction product of a monoisocyanate compound with at least one kind of vegetable oil selected from castor oil and lesquerella oil as a polyol component.