Mn(Sb-Bi) alloy films with NiAs-type structure were prepared by successive deposition of Mn layer onto Sb-Bi alloy layer, followed by annealing up to 500°C The single phase of NiAs-type was obtained in the wide composition range, 52≤Mn≤62 at.%, 35≤Sb≤48 at.%, 0≤Bi≤5 at.%. Systematic experimental investigation for the magnetic and magnetooptical properties was carried out for these films. As a result, (1) the dependences of Ms, Hc and Ku on composition and, (2) the dependence of θK on composition and also on λ (0.4∼1.1 μm) were systematically clarified. The magnitudes of Ms and θk were dependent on Mn composition. Maximum values of Ms and θK were 600 emu/cm3 and 0.7° (λ=0.633 μm), respectively for films with around 52 at.%Mn. The positive maximum value of Ku (nearly equals 1×106 erg/cm3 was obtained for films with about 62 at.%Mn.