An optical isolator surface−mountable, having a high heat resistance temperature and an improved reliability, and not requiring any adjustment of the optical axis of the polarizer when assembling the optical isolator. In the optical isolator, a first polarizer (18a), a Faraday element (12), and a second polarizer (18b) are arrayed in this order along the optical axis, and a permanent magnet (10) for applying a magnetic field the direction of which is along the optical axis to the Faraday element is disposed outside the Faraday element (12). The permanent magnet is U−shaped. In the inside space, the Faraday element is secured, thus fabricating a Faraday rotator assembly (16). The first and second polarizers are secured to a holder plate (20) at intervals, thus fabricating a polarizer assembly (24). The Faraday assembly and the polarizer assembly are so assembled into one unit that the edge faces of both legs of the permanent magnet face to the upper side of the holder plate.
