Electrochemical signal current can be enhanced by increasing surface area of the electrode or integrating nanopores at the electrode surface. However, complex processes have limited wide-application of nanoporous electrodes. We present a simple method enhancing redox current signal of electrochemcal sensors based on carbon electrodes using oxygen plasm treatment. The carbon electrodes are fabricated using carbon-MEMS process consisting of conventional photolithography and pyrolysis. Micro-sized pores and wrinkles are generated on the surface of negative photoresist structures patterned using an oxygen plasma treatment ahead of pyrolysis. The porous polymer structures were converted into carbon electrodes with nano-sized wrinkles and nanopores via pyrolysis. The geometry of the carbon electrode is determined by the photolithography so that complex shapes of micro/sub-micrometer-sized carbon electrodes can be fabricated. Moreover, the sizes of the carbon nanopores can be controlled depending on the conditions of the oxygen plasma treatment and pyrolysis processes. The electrochemical currents of disc carbon electrodes were enhanced up to 2.6 times compared to a bare carbon electrode by just applying a 200s oxygen plasma treatment before pyrolysis. We expect this novel nanoporous carbon electrodes to be used in a variety of applications of bio-sensors such as sandwich immuno-assay, enzyme-based sensors and non-enzymatic bio-sensors.