To polish rifle grooves like a new product by sliding the protrusion parts of a plurality of hone bodies to the rifle grooves in a gun tube.

An inner end of each hone holding body is slidably contacted with a taper surface of a taper member 15, each hone body comes in and out along the radius direction of a cylindrical base 10 by the movement in the axial direction B of a taper member 15, and the pressing force of the hone body to the gun tube 5 is adjusted by the energization of an elastic body. A surface of the hone body is uneven, and formed by a plurality of protrusion parts 11a and recess parts, the protrusion parts 11a are slidably contacted with the rifling grooves in the gun tube 5, and the hone bodies are respectively rotated along the rifle grooves with a cylindrical base 10 by the movement in the axial direction B of this hone bodies to clean and polish the rifle grooves.