Bi_2.5Y_0.5Fe₅O₁₂ and Bi₃Fe₅O₁₂ thin films were prepared on Gd₃Ga₅O₁₂ substrates using a metal organic decomposition (MOD) method as magneto-optical indicators (MOI) to visualize the distribution of magnetic flux. Their structural and magneto-optical properties were studied. The Faraday rotations of Bi_2.5Y_0.5Fe₅O₁₂ and Bi₃Fe₅O₁₂ thin films were 15.5 μm/degrees at a wavelength of 524 nm for the former and 23.0 μm/degrees at 530 nm for the latter. We found that these films prepared by MOD were suitable for MOI, because of their large Faraday rotation, in-plane magnetic anisotropy, and extinct magnetic domain structures.