To provide a device which can online-conduct the surface polishing of a rubber lining roll.

This polishing device consists of a straight brush 1 with a hair material 11 disposed closely along the lengthwise direction, and a supporting device 2 disposed at a prescribed position. The hair material 11 of the straight brush 1 is disposed over the overall length of a rubber lining roll R and closely along the axial direction. The hair material 11 is formed by mixing abrasive grain with aromatic polyamide resin. By rotating the roll R with the top end of the hair material brought into contact with the surface of the rubber lining roll R, the roll R surface is polished.