We present here a method for the electrochemical enrichment of chromium-reducing bacteria from environmental samples containing various microorganisms. An electrochemical cultivation system was constructed; this consisted of a Pt anode and a carbon cathode separated by an ion-exchange membrane. For an electrochemical cultivation, an environmental sample with chromium-reducing bacteria was inoculated into the anode well where a medium containing 0.1 mM Cr(VI) ions was poured. On the other hand, Cr(VI)-free medium was poured into the cathode well. Chromium-reducing bacteria grew selectively after 10 days of incubation and application of 1.0 V (vs. Ag/AgCl) of anode potential that reproduces Cr(VI) ions. This result suggested that Cr(VI) ions generated on the anode promoted the growth of chromium-reducing bacteria as their electron acceptor and due to Cr(VI) toxicity, inhibited the growth of other microorganisms.