Provided is a set screw for antibacterial device to be implanted in vivo, comprising a set screw main body having a threaded groove provided on the outer periphery thereof and a hole part provided on the head thereof, a cap having a leg part that fits into the hole part of the set screw main body, wherein the surface of at least the hole part of the set screw main body and the surface of at least the leg part of the cap include a first material and a second material having a potential difference, the first material includes an antibacterial metal, the second material is more precious than the first material, when used implanted in vivo an electrical circuit is constituted between the first material and the second material, ions of the antibacterial metal are eluted from the first material in the presence of an electrolyte, generating a bactericidal activity on the surface and/or in the vicinity of the surface of the first material.
