A method of producing a decellularized transplantation material, wherein the method includes the steps of (a) harvesting a branch-bearing blood vessel from a vertebrate animal (a donor)； (b) decellularizing the blood vessel； and (c) adhering, by a protein denaturation treatment, a portion where a branch has been excised to close the vessel. Also, a graft composition consisting of a biocompatible material that contains the decellularized transplantation material.
