The invention discloses an electrolysis device and method for efficiently extracting slag inclusion in steel, and belongs to the technical field of metallurgical engineering. The device comprises a power supply, an electrolytic bath, a seal cover and a temperature gauge and further comprises a cathode, at least two anodes, at least two anode rotating devices, a center rotator, an insulating support and an anode connecting frame. The electrolytic reaction area is increased through increasing anode sample number and adopting a sample parallel connection mode, and at the same time, the electrolysis is accelerated through sample rotating; same or opposite rotation direction between the anode and a center stirrer is guaranteed, and the slag inclusion in partial electrolyzed steel sample is rapidly separated from the steel sample and mass transfer by a molten pool is accelerated through controlling the rotating speed of the anode and controlling the rotating speed of the center stirrer, so that the nodulation of the sample surface is avoided, and the electrolytic efficiency is improved; a conductive metal gas-guide tube in which air holes are formed is adopted by the cathode, and argon is introduced and enters the electrolyte through the air holes, so that the stirring effect is improved; and at the same time, inert gas guarantees that the electrolyte is in an oxygen-free state, so that the anodes are prevented from being oxidized by oxygen in air.