The present invention relates to a composition for a biodegradable fiber and a biodegradable fiber manufactured using same. In detail, according to an embodiment of the present invention, the composition for biodegradable fibers contains a polyhydroxyalkanoate (PHA) resin bearing 4-hydroxybutyrate (4-HB) repeating units and specifically a first PHA resin and/or a second PHA resin, each bearing 4-HB repeating units and meets a degradation temperature (Td 5% weight loss) of 220°C or higher as measured by a thermal gravimetric analyzer. Thus, the composition is eco-friendly with excellent biodegradability and biocompatibility and can be used to easily manufacture biodegradable fibers having excellent properties.