The feasibility of microwave sintering of electronic ceramics was investigated using a heating control system. This system comprises a klystron amplifier with 6 GHz band, a single mode rectangular cavity for sintering ceramics, and a controller for operating the heating condition. Eight kinds of electronic ceramic powders, Al₂O₃, AlN, TiO₂, stabilized ZrO₂, ZnO, PZT, PLZT, and BaTiO₃, were prepared as test samples. These powders were compacted into a cylindrical form of 6.6 mm diameter, followed by cold isostatic pressing (CIP). Then, they were sintered in the cavity with either air or nitrogen gas. ZnO and stabilized ZrO₂ were easily sintered in air, and their densities were the same as the theoretical densities. Especially, ZnO could achieve a high density of over 95% of the theoretical with a sintering time of only 5 sec. On the other hand, the microwave sintering of PZT, PLZT, and BaTiO₃ was difficult because uneven heating and melting occurred due to thermal runaway. However, by covering the samples with a silicon carbide tube, the thermal runaway could be prevented. The sintered PZT had uniform microstructure with over 98% of the theoretical density.