[en] We discuss CP violation in a massive Majorana neutrino system. In general, for the n-Majorana neutrino system (n = number of generations) the number of CP-violation phases is n(n-1)/2 in contrast to the Dirac neutrino system where (n-1)(n-2)/2 phases are present. Therefore, the CP-violation effect appears even in the case of two generations. For neutrino oscillations, however, this number reduces to (n-1)(n-2)/2 due to the special combination of the unitary transformation matrix among the current neutrinos (ν) and mass neutrinos (N). (orig.)