The electrodeposition of cobalt–antimony thermoelectric semiconductor films was investigated in a non-aqueous solution of ethylene glycol (EG)–CoCl 2 –SbCl 3 at 393K. By controlling the bath composition and cathodic current density, Co–Sb alloys containing 0–94mol% of Co were obtained at 50–300 Am −2 . The resistance polarization caused by the formation of semiconductor film was observed in the polarization curve measured in the EG–CoCl 2 –SbCl 3 (90.0–9.3–0.7mol%) bath. In this bath, the Co–Sb (23.6–76.4mol%) alloy was obtained by maintaining the constant potential electrolysis at 0.1V. This alloy included CoSb 3 and exhibited a p-type thermoelectric conversion by the given temperature difference.