For the purpose of investigating the origin of the magnetic anisotropy in the Fe‐Ni based amorphous alloys, we studied the temperature dependence of the magnetic anisotropy, defined as the energy required to saturate the magnetization. It is concluded that the anisotropy of the as‐quenched alloy is most likely due to the internal stress field, and the field induced anisotropy is presumably due to short range atomic pair ordering.