A method of improving elasticity of a tissue of a living body, the method including: forming a through-hole in the living body; inserting an insertion path forming unit, which includes a pipe member including a pipe and a support member including a support rod, into the through-hole in a state where the pipe member and the support member are assembled; removing the support member from the insertion path forming unit; coupling a medical thread supply unit to the pipe member; pushing the medical thread from behind by using a push unit; and removing the push unit, the medical thread supply unit, and the pipe member.