Current wastewater treatment technology has some problem concerning the environmental load. For example, the activated sludge process of aerobic wastewater treatment requires the large consumption of electricity and the high excess sludge disposal cost. The methane fermentation process of anaerobic wastewater treatment is energy saving technology, but this system has problem of diffusion of dissolved methane in effluent (Methane has a global warming potential of 23). For the solution of these problems, development of new wastewater treatment system is necessary. Utilization of microbial fuel cells (MFC) has attracted attention as new generation wastewater treatment technology. MFC is a kind of fuel cells using bio-catalyst, this technology generate electricity from biodegradation of organic matter. It is anticipated that excess sludge and treatment energy are less than conventional wastewater technology. Additionally, wastewater is converted efficiently into electricity. However, MFC system is far-out technology on wastewater treatment. In this study, a single chamber MFC that is energy saving system of MFC was applied to the continuous operation of synthetic wastewater, in order to evaluate the efficiencies on electricity generation and on organic treatment.