In an apparatus and method for magnetic field assisted electrochemical discharge machining (ECDM), the magneto hydrodynamic (MHD) effect is utilized to improve the thickness of bubble film and the electrolyte circulation so as to enhance the machining accuracy and efficiency. Since charged ions in a magnetic field are induced by Lorenz force to move, and the electrolysis bubbles generated in the ECDM process are suffused with electrification ions on their surfaces, the electrolysis bubbles can be forced to move in the direction of the magnetic field without the need of mechanical disturbance. The present invention can be widely applied in the micro-machining of non-conductive brittle materials of different dimensions and shapes, comprising the forming of microchannels and microholes on a biochip, and in the micro-opto-electro-mechanical system (MOEMS) and various kinds of micro-machining fields. The machined surface is smooth and does not require a second time machining.