It is pointed out that the measurement of the static magnetic susceptibilities over a wide temperature range will be able to give the detailed information about the electronic structure of the paramagnetic heme derivatives. On the basis of the data given by the electron paramagnetic resonance experiment, formulas for the temperature dependence of the effective magnetic moment (neff) of the ferrihemoglobin fluoride and the ferrihemoglobin azide are derived; further the temperature dependence of neff of the ferrohemoglobin is studied theoretically and it is shown from the observed value of neff at room temperature that the non-cubic ligand field is weaker in the case of ferrohemoglobin compared with the case of ferrihemoglobin azide.