A bioactive platform with a carbon composite electrode was developed for rapid detection of Escherichia coli O157:H7. The porous carbon composite electrode was prepared by a sol-gel method with a mixture of graphite powder and tetraethyl orthosilicate/ethanol. Escherichia coli O157:H7 antibodies were physically adsorbed onto the carbon composite electrode. Direct measurements by cyclic voltammetry and electrochemical impedance spectroscopy in the presence of [Fe(CN)6]^3-/4- as a redox probe showed that the immobilization of antibodies onto the carbon composite electrode surface and the binding of Escherichia coli O157:H7 cells with antibodies systematically increased the electron-transfer resistance. Those results suggest that a sol-gel derived graphite composite electrode might be utilized as a label-free electrochemical immunosensor for diagnosis, biochemical research, food industry, and so on.