Magnetization measurements and differential thermal analysis (DTA) of polycrystalline MnBi were carried out in magnetic fields up to 14 T and in 300-773 K, in order to investigate the magnetic phase transition. The magnetic phase transition temperature (T t ) at a zero magnetic field is 628 K and linearly increases with increasing fields up to 14 T at the rate of 2 KT À1 . A metamagnetic transition between the paramagnetic and field-induced ferromagnetic states was observed just above T t . The exothermic and endothermic peaks were detected in the magnetic field dependence of DTA signals in 626-623 K, which relates to the metamagnetic transition. The obtained results were discussed on the basis of a mean field theory