Abstract: A catalyst used to manufacture a biodegradable polyester resin, in particular, an organic titanium catalyst which does not contain a heavy-metal component, and a method of manufacturing a polyester resin using the same. Accordingly, the method of manufacturing a polyester resin can be useful in attaining desired physical properties without using a catalyst harmful to environments and a human body. The biodegradable resin, which can be safely used in the field of applications in which the use of harmful components is a sensitive issue without using the components harmful to environments and a human body during the manufacture of a resin, can be prepared.