An optical module is provided that includes a Faraday rotator having a Verdet constant at a wavelength of 1.06 μm of at least 0.27 min/(Oe·cm), a first hollow magnet disposed on the outer periphery of the Faraday rotator, and second and third hollow magnet units disposed so as to sandwich the first hollow magnet on the optical axis. The second and third hollow magnet units include 2 or more magnets equally divided in a direction of 90 degrees relative to the optical axis. A magnetic flux density B (Oe) applied to the Faraday rotator is in the range of 0.5×104≦B≦1.5×104. The Faraday rotator is disposed on a sample length L (cm) in the range of 0.70≦L≦1.10, and has an external diameter D (cm) in the range of 0.20≦D≦0.60.