PURPOSE: To produce a polyurethane excellent in hydrolysis resistance and suitable for use in soles, by reacting a polyesterdiol with a diol, a blowing agent and a diisocyanate in the presence of a compound having three active hydrogen atoms.

CONSTITUTION: A mixture of a polyesterdiol of MW of 500W4,000, prepared by reacting adipic acid with (di)ethylene glycol, etc., a diol of MW of 62W400 (e.g., ethylene glycol), and a blowing agent (e.g., water) is reacted with a diisocyanate and/or an isocyanato-terminated prepolymer prepared from a diisocyanate and a compound having two active hydrogen atoms in the presence of a compound having three active hydrogen atoms (e.g., trimethylolpropane) in an amount of 0.001W0.070mol per 1,000g of the polyurethane to be produced.