The redox reaction of cytochrome c immobilized on the bare surfaces of microelectrodes and macroscopic electrodes (macroelectrodes) composed of different planes of highly oriented pyrolytic graphite has been investigated using cyclic voltammetry. The protein-immobilized microelectrodes were fabricated using a simple masking method. For both macroelectrodes and microelectrodes, the redox reaction of immobilized cytochrome c needs to be activated by increasing the electrochemical potential maximum of cyclic voltammetry to a high positive value. The redox currents of this protein- electrode system can be enhanced using two approaches. The oxidation and reduction currents of cytochrome c adsorbed on microelectrodes that are composed of the edge plane show an anomalous enhancement compared to those for macroelectrodes composed of the basal plane. The difference in the surface chemical properties of the two kinds of electrodes results in the current anomaly. The oxidation current of the macroelectrode can be selectively enhanced by decreasing the potential minimum.