Diamond thin films were formed by deflecting the flow of CH+4using a magnetic field. The possibility of involvement of neutral particles and their effects on film formation were examined. The results show (i) the estimated amount of the neutral particle involved during the ionized deposition was nearly 30%, (ii) the surface morphology of the film prepared by the deposition of the deflecting ion was very smooth when it was examined by scanning electron microscopy, and (iii) transmission electron diffraction and transmission electron microscopy indicated relatively large grain polycrystalline diamond films.