||In general, fibers of nylons have widely been used as a fishery net. When they are wasted in a sea, they do barely biodegrade, which causes serious environmental problems. Polybutylene succinate (PBS) is one of the promising biodegradable polymers and can be used in fishery net instead of nylon due to their comparable mechanical properties. It is desirable to develop better treatment methods for degrading since it degrades all over several years. Surfactant has both hydrophilic and hydrophobic portions. If PBS is treated with surfactant before biodegradation, hydrophobic portion is attached to PBS and the hydrophilic portion is attached to the microorganism. This not only promotes better penetration of microorganism, but also water itself, facilitating biodegradation. In this study, PBS fiber was biodegraded in seawater condition with Paenibacillus sp. Tween-80 was used as surfactant due to their non-toxic and non-ionic properties and biodegradation mechanism of PBS could be predicted.