Provided are an apparatus and a method for rapidly producing a synthetic gas from a bio-diesel byproduct using microwave plasma, in which, while a plasma flame is generated by a plasma generator and waste glycerin, a bio-diesel byproduct, as fuel, is gasified by being supplied to the generated plasma flame of high temperature, the fuel is supplied in various types to increase the contact time or the contact area with the plasma flame and thus promote gasification thereof and the contents of steam and oxygen supplied and the plasma power are controlled to increase the collection amount of combustible gas and thus allow rapid production of the synthetic gas.