A tube-structured battery to be inserted into a living body is provided. The tube-structured battery includes: a biofuel battery part which generates electric energy by using biofuel in the blood passing through an internal space of the tube structure; a transformer circuit part which adjusts a voltage or current density by using the generated electric energy; and a secondary battery part which is charged with the electric energy by using the adjusted voltage or current density to store the electric energy, wherein the tube-structured battery is inserted into the living body or a blood vessel of the living body.