PURPOSE: To remove a fine burr from a molded article and stabilize its quality, by concurrently performing injection of high pressure water in a process injecting a polishing material.

CONSTITUTION: The method first rough finishes a surface and a burr 7, 8 in the inside of a molded article 9, set onto a rotary table 6, by injecting high pressure water from a nozzle 5 next finishes the surface and the burr in the inside of the molded article by mixed liquid of a polishing material in water from a nozzle 1W4. The method finally removes a fine burr from the surface and the inside of the molded article cimultaneously a polishing material and burr residue or the like adhering to the article by injecting the high pressure water from the nozzle 5.