To provide a combustion efficiency boosting device, installed on an internal combustion engine for an automobile, boiler, etc., in which heat efficiency of an engine is increased even when fuel is consumed under the same conditions to improve energy saving effect and fuel consumption performance, and minimize soot, while contributing to natural environments.

This device is installed in a fuel tank as immersion type for boosting combustion efficiency. It is composed of a core rod 10 composed by applying or impregnating ceramic powder 12 around silver alloy 11, and sealing it with aluminum alloy 13, and an inner electrode to exchange electrons with contact surfaces of fuel surrounding the core rod 10 to generate potential difference. Water contained in fuel is set at reduction potential through electromagnetic waves and electromotive force by the core rod 10 and the inner electrode.