The invention discloses a microwave water heater which comprises an inner tank, a microwave heating system, a microwave generation auxiliary device and a heat dissipation structure, wherein the inner tank is used for storing water; the microwave heating system is arranged outside the inner tank; the microwave generation auxiliary device is arranged outside the inner tank and is used for driving the microwave heating system to emit a microwave to the inside of the inner tank to heat the stored water in the inner tank; and the heat dissipation structure comprises an insulating heat-conducting material which is connected to the microwave generation auxiliary device and the inner tank to emit heat to the stored water in the inner tank. The heat generated by the microwave generation auxiliary device is transmitted to the inner tank through the insulating heat-conducting material to heat the water in the inner tank, thereby achieving recycling of energy and achieving the energy-saving target. Meanwhile, the microwave water heater is capable of emitting head of the microwave generation auxiliary device without adding a heat dissipation device, so that the energy consumption is further reduced.