[en] The first observation of the pressure-induced transition from the antiferromagnetic to the ferromagnetic SrFeO₃ was succeeded by measuring Moessbauer spectroscopy under high pressure produced by the diamond anvil cell (DAC). Sample is a polycrystal powder of antiferromagnetic SrFe0₃ with the Neel temperature T_N=140 K, the cubic system and perovskite type crystal. The average pressures used were 44 GPa and 74 GPa (300 K). SrFeO₃ is paramagnetic material at 300 K, but the Neel temperature increases more than 300 K under high pressure and the quantized axis turns to the external magnetic field, so that we take it as it means the system displaying the phase transition to the ferromagnet. By the method, we can practice the measurement at low and high temperature under the external magnetic field by using the polarized light source. (S.Y.)