YVO4:Eu3+ and Mg2SnO4:Mn2+ phosphors were prepared using a domestic microwave oven. The temperature of the raw materials irradiated with a microwave was rose up to 1111-1716 K within 150 s, followed by a sharp drop in the temperature in spite of irradiating the microwave continuously. A low dielectric loss factor of the reaction products caused the sharp drop in temperature as soon as the reaction was completed.