To provide a recycling method of polishing slurry capable of recycling used slurry used in a semiconductor wafer polishing process, in particular, a final polishing process, and of reducing manufacturing cost of a semiconductor wafer by remarkably reducing slurry usage.

This recycling method of polishing slurry used for recycling used slurry prepared by including colloidal silica, and used in the polishing process of a semiconductor wafer is characterized by executing: a process S7 of adding a dispersant in recovered used slurry to prevent gelation of the used slurry; a process S8 of irradiating the used slurry with the dispersant added therein with ultrasonic waves to disperse the gelated slurry and aggregated silica; and a process S9 of removing a foreign substance in the used slurry after ultrasonic wave irradiation by a filter.