Disclosed herein is a microwave heating device. A material conduit runs into and out of a microwave irradiation cavity through a cavity wall of the microwave irradiation cavity. A waveguide tube for guiding microwave is installed on the cavity wall. A heat exchange tube is disposed inside the material conduit and enters and leaves the material conduit from the nozzle or wall of the material conduit. The microwave heating device is used in chemical reactions. The microwave heating device may control the temperature of the material inside the material conduit under continuous irradiation of microwave.