PURPOSE: To reduce the surface scratches of a product and stably manufacture a seamless steel tube excellent in surface quality by rolling a rolled stock continuously as it is supplied to the following stage after the outer surface of the rolled stock is ground in a hot state in conveying after it is passed through a piercing stage or a drawing stage.

CONSTITUTION: After the surface scratches caused in the piercing or drawing stage are eliminated completely, the rolled stock 1 is supplied to the following stage. The surface scratches of the rolled stock 1 are ground at a piercing roller and a drawing roller or a drawing roller and the following roller because it is effective to remove the scratches while it in small immediately after they have been caused. Since a grinding device used is a rotating rolled stock 1 of steel tube and it is in a special condition of a high temperature of about 1000°C, the grinder stone 2 is rotatable and cylindrical one and is used as it is cooled by water through a nozzle 4. Further, the whole surface of the steel tube need not be ground and no more than local repair of scratched parts only is required.