Some biodegradable polymers of as poly(γ-lactone) and poly(succinate) were surface-treated by glow discharge plasmas under an appropriate condition, and the effects were investigated with respect to the weight loss, surface morphology change, and bio-degradation. The weight loss rates by oxidative plasmas were in general higher than those for a polyester sheet made of poly (ethylene terephthalate). After glow discharge treatments, the characteristic surface morphology appeared by the observation of scanning electron microscopy (SEM). Surface became more wettable, and activated by plasma treatments. Bio-degradation of these polymers was investigated in composts under appropriate condition, and the effects were discussed.