A method for manufacturing a readerwriter is provided having a substrate with an undercoat formed thereon. The present invention is to provide a method of producing a variable resistance memory element whereby the lower electrode can be formed smaller. The apparatus includes an input unit for inputting machining conditions relating to the jump conditions in precedence to machining, and a numerical control unit for determining various parameters in dependence on the machining conditions. Slotted openings in the narrow sides act as entrance and exit ports for a conveyor transporting a product along a conveying path through the chamber perpendicular to the propagation direction and perpendicular to the electric field. The preferred embodiment uses a plurality of optical couplers, with partitions to establish a serpentine path around the couplers for comprehensive exposure to the fluid.