To provide a method to certainly remove burr and mill scale of a precision part underwater, at low cost and in a short period of time without making a flaw on a surface of a work.

The burr and the mill scale are instantly removed as high pressure treating water entrains a media and collides against the work at high speed, by previously putting the spherical particulate media containing spherical zircon beads a grain diameter of which is about 40 μm to about 800 μm underwater and injecting the high pressure treating water from an injection nozzle underwater.