We fabricated Fe-silicide nanodots (NDs) on an ultrathin SiO₂ layer and evaluated changes in electron transport properties with and without magnetic field application. High-density NDs with an areal density as high as ∼10¹¹cm^-2 were formed on thermally grown SiO₂ by exposing ultrathin Fe/Si-NDs structures to a remote H₂ plasma without external heating. In electron transport properties related to current-time characteristics for a diode with Fe electrode and charging energy to NDs, clear changes in current levels through NDs and electron injection modulation of NDs depending on intensity of magnetic fields were observed.