Poly(ethylene oxide)-modified myoglobin (PEO-Mb) was coated on an indium tin oxide (ITO) electrode, and the electrochemical redox reaction of PEO-Mb was confirmed by means of visible electrochemical redox reaction of PEO-Mb was confirmed by means of visible spectrophotometry and cyclic voltammetry. The PEO-Mb coated on the ITO electrode surface transferred electrons when the scan rate was greater than 0.4 mVs-1. The electron transfer between PEO-Mb molecules in the PEO-Mb multilayer occurs when a negative potential (-1.5 V vs. Ag) is applied continuously to the ITO working electrode. After reduction of PEO-Mb, a positive potential (+ 1.5 V vs. Ag) was applied to the ITO working electrode to re-oxidize the PEO-Mb. Reduction and re-oxidation were carried out repeatedly but incompletely, probably because of a very slow electron transfer between adjacent PEO-Mb molecules in the coated layer. Since well-defined redox waves were observed in the cyclic voltammograms for PEO-Mb coated on an ITO electrode even at 72-degrees-C, the thermal characteristics of PEO-Mb appear to have been improved. It was also confirmed that the redox reaction was reversible over a wide temperature range (25-72-degrees-C).