The magnetic anisotropy of a 50% Ni-50% Fe alloy, after (1) cold reduction and (2) cold reduction and annealing at various temperatures, has been determined from magnetic torque curves, from which the types of the rolling and recrystallization textures in the specimens have been deduced. In the specimens with perfect cube texture, the magnetic anisotropy constant k1 has been determined; the result is consistent with that of other authors' using single crystal specimens. The k1 value in the cold rolled specimens is, however, larger. The factors which may possibly influence the determined k1 values are considered; the influences due to the degree of ordering and the elastic energy induced by anisotropic magnetostriction are finally discussed.