Manganese nitride films were fabricated on MgO substrates by changing N2 flow ratio into Ar gas (P N 2) during reactive sputtering deposition of the films, and their crystal structures and magnetic properties were investigated. Single phased ε-Mn4N films were obtained when P N 2 was 5%-9%, and the tetragonal lattice distortion was identified in all the Mn4N films (the lattice constant ratio, c/a = 0.99). Perpendicular magnetic anisotropy was observed in all the specimens. The Mn4N film, fabricated with P N 2 = 8%, has a low saturation magnetization (Ms = 110 emu/cc) and relatively high magnetic anisotropic energy (Ku = 8.8 × 105erg/cc). Both Ms and Ku of the films drastically changed with mixing other phases (α-Mn, β-Mn, η-Mn3N2, and possibly γ-Mn) by varying P N 2.