An optical fiber penetration is disposed in a sleeve provided through a partition wall that separates a first space and a second space. The optical fiber penetration includes a first optical fiber cable and a second optical fiber cable each having a thin tube formed of metal and an optical fiber strand inserted in the thin tube, a cylindrical body that is formed of metal and is disposed in an axial direction of the sleeve, an interior of which includes the first optical fiber cable on a side of the first space and the second optical fiber cable on a side of the second space, an internal connector configured to connect the first optical fiber cable with the second optical fiber cable in the interior of the cylindrical body, and a first lid and a second lid configured to close one end and the other end of the cylindrical body.