The tree surgery method includes a decayed-tissue removing step of removing a decayed tissue of a cavity and exposing a solid woody tissue; an internal treating step of performing sterilization and insecticidal treatment on the woody tissue and drying the woody tissue; a protective layer forming step of coating the woody tissue with a protective agent to form a protective layer; a cambium exposing step of cutting out an edge of the cavity and exposing a cambium; a cavity filling step of filling the cavity on which the protective layer is formed with a urethane foam, and an artificial-tree-bark forming step of filling and coating an upper surface of the urethane foam with a tree bark material including a mixture of cork powder and silicone sealant to form an artificial tree bark. The tree bark material includes a mixture of colored silicone sealants allowing a color similar to real trees.
