Provided is a polyurethane polymer which is excellent in oil resistance, weatherability, light resistance, heat resistance, hot water resistance, hydrolysis resistance, strength, chlorine resistance, and chemical resistance, and which can be produced simply and economically. The polyurethane polymer is produced by polymerizing at least two components: a vinyl polymer (A) having a mercapto group at each end of the molecular chain produced by a reversible addition-fragmentation chain transfer polymerization method, and an organic polyisocyanate (B). Also provided are polyurethane-based materials containing the polyurethane polymer, and polyurethane elastic fiber.