PURPOSE: To provide the method for joining sheet bars by rotationally sliding inserts in which the sheet bars are joined by rolling on the inlet side of a finishing mill at the time of fully continuous hot rolling.

CONSTITUTION: A gap 25 is provided between abutting faces at the tip part of the succeeding sheet bar 12 and rear end part of a preceding sheet bar 13 and, cylindrical insert materials 14 are inserted into this gap. After rotationally sliding the insert materials while depressing the insert materials with the sheet bars in rolling, the insert materials are reduced in the thickness direction while preventing the enlargement of the gap and the tip part of the succeeding sheet bar and rear end part of the preceding sheet bar are joined. In this way, the adhesion strength in the interface between the sheet bar and the insert material is enhanced, so the sheet bars are firmly joined by rolling and it is achieved to make the equipment compact, so productivity in sheet bar rolling is improved.