Transformation from perovskite to post-perovskite was observed in MnGeO3 and MgGeO3 in the Kawai-type apparatus equipped with sintered diamond anvils by means of in situ X-ray diffraction method. In MnGeO3, post-perovskite phase was observed at 63.5 GPa and 1233 K. The transition pressure was ∼6 GPa higher than previous report by the laser heated diamond anvil cell experiment. In MgGeO3, we observed the transformation from perovskite to post-perovskite and the reversal transformation under the conditions of 61-64 GPa and 1100-1700 K. The phase boundary was determined to be P (GPa) = 5.2 × 10-3 T (K)+55.2, where P is pressure and T is absolute temperature, which is almost consistent with previous result by diamond anvil experiments. However, reliable pressure standard is needed to determine the boundary precisely.