Monte Carlo simulation of the C 60 -fullerite film irradiation by 5 keV electron beam at normal incidence has been performed. Average transverse coordinates of the primary and secondary electrons as well as the density of collisions of several types were drawn in dependence on the penetration depth. It was shown that a swarm of low energy secondary electrons provides efficient excitation of valence electrons and gives the main contribution to polymerization of C 60 -fullerite.