PURPOSE: To provide the subject polymer improved in modulus characteristics without depending on the increase of hard segment component, by reacting an organic polyisocyanate, an organic polyol having a specific molecular weight, a bifunctional isocyanate reacting compound, and a chain extending agent.

CONSTITUTION: (A) An organic polyisocyanate (e.g. 4,4'-methylenebis(cyclohexylisocyanate) or the like), (B) an organic polyol having a molecular weight of 1,000-12,000 (e.g. polyether polyol or the like), (C) a bifunctional isocyanate reactive compound having a molecular weight of 350-550 (e.g. polyethylene oxyglycol or the like) and (D) A chain extending agent having 2-3 functional groups (e.g. ethyleneglycol) are reacted in ratios of these four components such that the ratio of isocyanate group to active hydrogen group is within 0.90:(1-1.15):1, thereby, the objective polyurethane is provided.