MnBi thin films have been studied as a magneto-optical memory element. Ordinarily, restricted conditions are required for preparing pure MnBi film with excellent properties and homogeneity. However, in the case of Mn-Bi-Te films, it was found that adopting the proper composition made it easy to prepare homogeneous films, and the figure of merit F/α was not worse than that of pure MnBi reported by other authors. Furthermore, the Faraday rotation was controlable by varying the composition of Mn-Bi-Te. Then, magnetic holograms were formed using the Mn-Bi-Te films exhibiting magnetization in a direction perpendicular to the film plane. The dependence of the diffraction efficiency on Faraday rotation and holographic writing conditions are reported.