For the isolation of CO2-fixing bacteria using electrochemical reducing power (ERP), a plate-type electrochemical bioreactor (PEB) was employed. Soluble neutral red (NR) was used as an electron mediator for carbonate-basal agar medium (CBAM) prepared in the PEB. For test of bacterial CO2 fixation using the ERP, a single-compartmented electrochemical bioreactor (SCEB) was employed. NR immobilized in the graphite felt cathode (NR-cathode) was used as an electron mediator for carbonate-basal broth medium (CBBM) prepared in the SCEB. Two bacterial genera capable of electrochemically fixing CO2 were isolated using the PEB and cultivated using the SCEB. The isolated bacterial species were 99% identified with Achromobacter sp. and Alcaligenes sp. Approximate 150 mL of CO2 per day was consumed by 300 mL of the mixed culture of Achromobacter sp. and Alcaligenes sp. grown electrochemically in the SCEB.