The enhancement of magnetization intensities in Na- and K-β″-ferrites by annealing in a chalcogen (S, Se) atmosphere was studied. Although Na- and K-β″-ferrites were changed to Na- and K-β-ferrites by annealing in a Se atmosphere (PΣSe = 31.4 kPa) at 1073 K for 1 h, the high magnetization intensities of 50 and 63 μWbmkg-1 respectively, were first obtained in Na- and K-β-ferrites. The enhancement of magnetization intensity is resulted from Se absorption into ionic conduction layer. It was indicated that Se atoms may occupy in two sites on the ionic conduction layer, because its TG curve showed two steps desorption process. K-β″-ferrite annealed at 1273 K in a Se atmosphere decomposed to cubic spinel and α-Fe2O3 phases, on the contrary, the K-β″-ferrite annealed in a S atmosphere decomposed to only the cubic spinel phase.