A bismuth-substituted rare earth iron garnet single crystal film is represented by a general equation Tb x Lu y Bi 3-x-y Fe 5-z Al z O₁₂ (where 0.09 ≦ y/x ≦ 0.23, 1.40 ≦ x + y ≦ 1.70, 0.20 ≦ z ≦ 0.38) grown on a non-magnetic garnet substrate (CaGd)₃(MgZrGa)₅O₁₂ having a lattice constant of 12.490 Å - 12.500 Å by a liquid phase epitaxial method. The bismuth-substituted rare earth iron garnet single crystal film satisfies three conditions that (1) the Faraday effect is large, i.e., the film thickness required for the Faraday rotator at a wavelength of 1.55 µm is 450 µm or less, (2) the saturated magnetic field is 800 (Oe) or less, and (3) the temperature coefficient α is 0.07 deg/°C or less.