A polybutadiene having a hydroxyl group at a terminal end thereof is reacted with a lactone compound such as an -caprolactone to obtain a polymer polyol represented by formula (I): HOX.sup.1YX.sup.2OH (wherein X.sup.1 and X.sup.2 each independently represents a polyester component and Y represents a polybutadiene component), the polymer polyol is reacted with an unsymmetric diisocyanate to obtain a urethane prepolymer, and then the urethane prepolymer is reacted with a chain extender to obtain a polyurethane.

A polybutadiene having a hydroxyl group at a terminal end thereof is reacted with a lactone compound such as an -caprolactone to obtain a polymer polyol represented by formula (I): HOX.sup.1YX.sup.2OH (wherein X.sup.1 and X.sup.2 each independently represents a polyester component and Y represents a polybutadiene component), the polymer polyol is reacted with an unsymmetric diisocyanate to obtain a urethane prepolymer, and then the urethane prepolymer is reacted with a chain extender to obtain a polyurethane.

A low-resilience polyurethane foam is obtained by causing a reaction of a raw material composition containing a polyisocyanate component and a polyol component, and the polyisocyanate component contains an n-functional isocyanate (n3) and a bifunctional isocyanate prepolymer. The polyisocyanate component preferably has an average number of functional groups of 2.05 or more. The polyol component preferably includes one or more high molecular weight polyols, and one or more low molecular weight polyols.