The Monte Carlo simulation is applied to the study of the diffusion phenomenon of hot electrons inn‐type GaAs. The model simulated is that the ensemble of electrons diffuses from the cathode toward the anode under the two‐valley semiconductor model, repeating the accelerations by the electric field and the collisions to the phonons. This electronic diffusion includes the electron transfer diffusion between valleys as well as the thermal diffusion in each valley. The electric field dependence of the electronic diffusion coefficient determined from the present new approach almost agrees with the Ruch‐Kino experimental result.