The method of electro-chemical processing of hydrocarbon substances, which includes the stage of conversion of those substances in a mixture with water or electrolyte solution by means of its processing with variable electric current. An electro-chemical processing is carried out by a two-stage treatment, comprising a primary electro-hydrodynamic processing by means of an exposure to high voltage, short-pulse electric current discharges of variable frequency, and also comprising the main electro-hydrodynamic processing, carried out in strongly whirling counterflows of the mixture, in the field with a high radial pressure gradient, by exposing the substance to an intensive cavitation, highly developed turbulence, acoustic pressure vibrations, high-frequency alternating electromagnetic field and secondary short-circuited electric currents induced in the conductive mixture, along with a simultaneous separation of the substances formed. The device for electro-hydrodynamic processing of hydrocarbon substances, containing a block for primary electro-hydrodynamic mixture processing is also described and claimed.