Provided are encoding and decoding stitching information generated when the 3D mesh model that is the non-manifold or non-orientable model is converted into orientable and manifold models upon encoding the 3D mesh information of the 3D mesh model. The method of encoding 3D mesh information includes the steps of: encoding the 3D mesh information to output an encoded bitstream; encoding stitching information of elements contained in the 3D mesh information, the stitching information having a total number of duplicated original elements and, for each of the duplicated original elements, the duplication number, original-element identification information and duplicated-element identification information; and generating a packet of the bitstream, wherein the encoded stitching information is inserted into the packet.