To provide a low density polyurethane foam without reducing mechanical strength with respect to a conventional polyurethane form.

Disclosed is the polyurethane foam which contains a polyurethane resin (U) having 0.001 to 0.04 μm2average surface area of a hard segment domains having 0 to 50% phase deviation measured by an atomic force microscope, wherein the polyurethane resin (U) is preferably formed by reacting an active hydrogen component (A) and a polyisocyanate component (B), and the component (A) is an active hydrogen component (A1) having a reaction rate constant of 1.44 to 40 when the component (A) and a phenyl isocyanate are reacted in xylene at 25°C at a ratio of an active hydrogen group/an isocyanate group=2/1 mol.

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