The invention discloses a regenerating method and device of a granular boronizing agent and belongs to the field of material surface modifying agent recycling. According to the technical scheme, the regenerating method comprises the following steps: placing a well pretreated basal body on an anode plate of magnetron sputtering equipment, and placing a high-purity silicon target on a copper back plate of a cathode by adopting a plane targeting manner; feeding argon gas into a vacuum chamber to wash the vacuum chamber and the well pretreated basal body; and then regulating power supply voltage and current density and vacuum air pressure. The regenerating method and device have the advantages that the boronizing effect of the regenerated boronizing agent reaches the boronized layer depth of the original boronizing agent and can be used for 3-5 times of the use number of the original boronizing agent; the coated boronizing agent has basically the same effect as the boronizing agent of original raw materials, and the boronized layer depth is at 120-130mm more or less; and the materials are saved, and cyclical green economical benefit is realized.