SnO2 films were implanted with 57Fe at substrate temperatures of room temperature and 300°C. The chemical states of Fe and Sn were characterized by 57Fe CEMS and 119Sn CEMS, respectively. The implanted Fe species exist as Fe(II) and Fe(III) in SnO2 films, which also are reduced into Sn(II)on the implanted surface. The as prepared and post annealed at 500°C samples did not show Kerr effect, but the sample implanted with 1 × 1017 Fe ions/cm2 at 300°C showed Kerr effect although magnetic sextets were not clearly observed in the 57Fe CEM spectra. The Kerr effect disappeared after annealing. It suggests that the number of magnetic defects decreases by absorption of oxygen. Magnetic relaxation appeared in the case of low implantation of 5 × 1016 Fe ions/cm2, which is considered to be due to anti-ferromagnetism or paramagnetic relaxation.