We have investigated effects of 1.2 MeV-Au++ ion irradiation into beta-FeSi2 samples which are synthesized by different processes. Such a high energy Au++ ion irradiation can be expected to induce Si and Fe vacancies in the beta-FeSi2 lattice. After recrystallization of the lattice, we found that one of the samples showed conversion from the initial p-type conduction to the n-type one. RBS analysis revealed that irradiated An atoms even after recrystallization by thermal annealing were not included in the beta-FeSi2 layers. These results suggest that the An atoms cannot contribute to conversion of the electrical conduction type observed. One possible explanation is that the highly induced Fe vacancy can play donor and its annihilation rate is much slower than that of Si vacancy that surely plays acceptor, so that carrier's compensation balance shifts toward n-type conduction. These results imply that vacancy-induction by high energy ion irradiation can be employed to control a conduction type of beta-FeSi2. (c) 2007 Elsevier B.V. All rights reserved.