To shorten the refining time in the refining of a pasty substance such as chocolate or butter.

This apparatus for refining a pasty substance has a refining tank 1 provided with a heater 3, a stirring blade 5 and a motor 4 for driving the blade 5. A microwave oscillator 7 (magnetron) is connected to the refining tank 1 through a waveguide 6 and the pasty substance 2 in the refining tank 1 is thoroughly stirred with the stirring blade 5. The component constituting the pasty substance 2 is agitated to a fine particle level by the microwave radiated from the microwave oscillator 7 to improve the stirring efficiency and shorten the time necessary for the refining process.