We describe a new method of sentinel node (SN) biopsy in the lower rectal cancer by a transsacral approach. Before the operation, an endoscopic clipping was performed around the tumor. The patient was placed in a jack knife position. A transverse incision was made over the S4-S5 joint. Subsequently, the S4-S5 joint was dissected, and the lower rectum was exposed without destroying the perirectal fatty tissue. CH-40 dye was injected into the submucosal layer of the rectal cancer. The lymph nodes that were blackened within 15 minutes were recognized to be SNs. Few investigations were reported with regard to sentinel node navigation surgery (SNNS) for lower rectal cancer, because the anatomical properties of the lower rectum make it difficult to inject the dye and recognize rectal tumors or lymph nodes. In our method, the lower rectum was exposed without destroying the perirectal fatty tissue, the dye was easily injected, and the SNs were easily found and extirpated. Our method of transsacral approach is considered to be useful.