To obtain the subject resin excellent in dyeability for a cationic dye and further excellent in dynamic characteristics, durability, processing characteristics, etc., by using a compound having a specific structure as a part of a component constituting a polyurethane resin.

This resin is obtained by copolymerizing a compound having a sulfonic acid quaternary phosphonium salt group which is preferably a 5-quaternary phosphonium sulfoisophthalic acid bisdiol ester represented by the formula (X is a 2-10C alkylene; R1 to R4 are each a 1-10C alkyl or the like) [e.g. 3,5-bis(2-hydroxyethoxycarbonyl)benzenesulfonic acid tetrabutylphosphonium salt] in an amount of 2.0-250 mol/106 g in a polyurethane resin. The resin is preferably obtained by reacting a polymer diol having 50-4,000 average molecular weight with the above compound, a low-molecular chain extender (e.g. ethylene glycol) and an organic diisocyanate (e.g. diphenylmethane diisocyanate).