the present invention provides an absorbable barrier membrane for guided tissue regeneration which is useful for regeneration of animal tissues , including those of humans , the absorbable barrier membrane being superior in heat stability , processability , reproducibility , storage stability , bioabsorbablity , and tissue regeneration effects , and further provides a method for regeneration , using the absorbable barrier membrane , of a mandible , periodontal tissue , or defective tubulous bone , and particularly a defective tubulous bone which possesses a segmental bone defect in which both ends of the bone are in separate segments . the above objects are attained by an absorbable barrier membrane for use in guided tissue generation , comprising a lactic copolyester in which a polymerization catalyst is deactivated , as an essential component .