The magnetic, the magneto-optical and the optical properties of Ni2MnIn alloy films with significantly different atomic orders (from nearly single-crystalline to amorphous) were investigated. The crystalline Ni2MnIn alloy films are a ferromagnetic with a Curie temperature of 325 - 330 K, while the amorphous phase is not ferromagnetically-ordered (at least, above 293 K). The diagonal and the off-diagonal components of the dielectric function for the crystalline alloy were experimentally determined for the first time. The nature of interband excitations in the optical spectra of the ordered phase is discussed in terms of the band structures of Ni2MnSn. The analyses of changes in the electron energy structure of Ni2MnIn alloy, caused by the structural disordering, are performed using the results of optical study. An annealing at 750 K for 2 hrs of the amorphous film restores its crystallinity (B2 phase) and also the ferromagnetic order.