A holder may include a base, an antenna and a sensor. The base has a bar shape extended along a central axis from a first end toward a second end. The base may include a metal member and a first resin. The metal member may include a pocket that is attachable of an insert including a cutting edge. The first resin may be located closer to the second end than the metal member. The antenna may be covered with the first resin. The sensor may be located closer to the pocket than the antenna and may be wired connected to the antenna, and may be measurable a state of the base. This configuration may contribute to solving the problem that handling of wiring becomes complicated.