In order to develop a new recycling process for neodymium permanent magnet generated in town, equilibrium relations between B2O3 slag, RExOy-B2O3 slag (RE = rare earths), and molten Fe-C alloy were experimentally investigated. When neodymium magnet was melted together with B2O3 and Fe-C alloy in graphite crucible, the sample was separated to 3 liquid phases of B2O3 slag, RExOy-B2O3 slag and molten Fe-C alloy. The concentration of RE in RExOy-B2O3 slag was increased with the decrease of the melting temperature, while that in B2O3 slag was increased with the decrease of the melting temperature. Cr, P, Ni, Co, and Cu were enriched in molten Fe-C alloy. Si and Al were enriched in B2O3 slag and RExOy-B2O3 slag. Utilizing such phenomena, a novel recycling process consisting of melting treatment with B2O3 and hydrometallurgical treatment using oxalic acid was proposed. The recovery rate of RE with the proposed process was over 99 %.