An optical isolator including a Faraday rotator that has a high Faraday effect and a high transmission factor in a wavelength used is provided. An optical isolator comprises at least: a Faraday rotator; a polarizer arranged on a light incidence side of the Faraday rotator; and an analyzer arranged on a light exit side of the Faraday rotator, wherein the Faraday rotator consists of an oxide that contains an ytterbium oxide (Yb2O3) with a mass ratio of 30% or more.
