We extended the attainable pressure of the Kawai-type multianvil apparatus to 71.3GPa and 120.3GPa at room temperature by equipping it with tungsten carbide (WC) and sintered diamond (SD) cubic anvils, respectively. In the experiments with WC anvils, pressure decreased largely, ΔP ∼−20GPa, on heating from room temperature to 1500K. In the experiments with SD anvils, pressure also dropped to 105GPa from 120GPa at 1673K. In order to generate higher pressure and temperatures, therefore, innovation of SD material in both quality and size are essential, together with improvements of cell assembly. Besides pressure generation, we conducted in situ energy-dispersive X-ray diffraction observations on CaSnO₃ and (Mg,Fe)SiO₃ in the experiments with WC and SD anvils, respectively. We observed the growth of new peaks, which can be assigned to the post-perovskite phase, transformed from a starting material of CaSnO₃ perovskite at 48.4GPa and 1500K, although they are not clearly identified. In contrast, we could not observe the post-perovskite phase of (Mg,Fe)SiO₃ in the present P–T conditions generated by experiments with SD anvils.