To provide a polyurethane-based elastic fiber having excellent elastic recovery characteristics, also having each excellent chlorine water resistance, resistance to yellowing by NOX and resistance to yellowing by chlorine, and good spinnability, and especially usable for a swimming wear used in a swimming pool or the like; and to provide a method for stably producing the polyurethane-based elastic fiber.

The polyurethane-based elastic fiber contains 0.1-3 wt.% hindered amine-based compound represented by chemical structural formula 1. The fiber is produced by subjecting a spinning solution containing the hindered amine-based compound to dry spinning.