In order to obtain exact values of the spectroscopic splitting factor in pure iron along the [100] and [111] crystallographic directions, measurements of ferromagnetic resonance in whisker type single crystals have been performed in the frequency range 12 + 70 GHz, at room temperature. The results show that the g-factor is independent on frequency in the given range and yield the value g = 2.089 ± 0.007 for both directions. A slight anisotropy of the surface magnetization has been found (M100 = 1 697.3 e. m. u./cm3 ; M111 = 1700.0 e. m. u./cm3) using the antiresonance measurement at 70 GHz