NOVELTY - The reactor has a main portion (2) consisting of a microwave impermeable material made of stainless steel, and a circuit of liquid raw material consisting of a mixture of fatty acids or fats and oils, and methanol (B). A microwave absorber such as activated carbon honeycomb (3) is installed in the circuit, and an impeller (4) is arranged to make liquid raw material circulate in the circuit in a fixed direction. A microwave generator (5) is set to irradiate microwave to microwave absorber.    USE - Microwave chemical reactor used in manufacture of bio-diesel fuel.    ADVANTAGE - The strength of the device main portion can be increased, and the liquid raw material which passes the microwave absorber can be made to quickly react on the interface with the absorber, while improving the stoichiometric reaction effect and the productivity of the fuel in less time. The attachment and detachment of the absorber with respect to the circuit can be performed easily, by forming the absorber in honeycomb shape. The discharge of acid or an alkali, and the need for neutralization and cleaning processes after the reaction are prevented, since the absorber consists of the specified catalyst. The gravity acting with respect to the liquid facing the microwave generator is suppressed by forming the initial and final portions of the pipe as specified, so that the microwave can be discharged without any disturbances. By attaching a reflux condenser, the raw material composition is stabilized, and the product can be removed from the drain, without changing the position of the apparatus. Since the whole absorber is submerged in the liquid raw material, the liquid raw material can be heated efficiently.    DETAILED DESCRIPTION - The microwave absorber having an acidic catalyst such as Lewis acid catalyst, alkali catalyst, such as Lewis-base catalyst is arranged such that it interrupts the circuit macroscopically, and the impeller is set with a rotating shaft arranged parallel to the circuit direction. Several U-tubes are mutually connected by a connecting pipe to form the circuit of a liquid raw material. The upper and lower ends of the initial and final portions of the connecting pipe are connected to the impeller. The internal diameter of the final portion of the pipe is larger than the initial portion of the pipe. A microwave permeable gas impervious filter (8) is provided to prevent penetration of gas generated within the main portion, into a microwave transmission source. The impeller blades are attached to the low-order rotating shaft rather than the connecting pipe. A reflux condenser (6) is attached between the upper end of connecting pipe and its final portion. A drain is attached to the bend section of the U-tube. An INDEPENDENT CLAIM is included for microwave chemical reaction method that involves fixing a microwave absorber to the position in circuit of a liquid raw material such that it is fully submerged in the liquid raw material and the height of the upper surface is less than 30 cm from the liquid level. The microwave is irradiated to the absorber when the liquid raw material is made to circulate in the main portion.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic block diagram of the microwave chemical reactor.    Main portion (2)    Activated carbon honeycomb (3)    Impeller (4)    Microwave generator (5)    Reflux condenser (6)    Microwave permeable gas impervious filter (8)    Methanol (B)