PURPOSE: To obtain the aligning method of steel sheets whose adjustment is controlled easily at the low cost by correcting misalignment of the steel sheets in accordance with the line center.

CONSTITUTION: In a seam welding line, the rear end 12a of a preceding steel sheet 1a and the tip 12b of a succeeding steel sheet 1b are superposed on each other and a couple of electrodes 5 hold the superposed part 13 of the steel sheets between them from the upper and lower sides to perform welding in the cross direction of the steel sheets. Side guides 7a and 7b of plate type to adjust separately the position of ends of the preceding and succeeding steel sheets are provided. Reference stoppers 8a and 8b Which can be moved and set at the desired position on the line center 10 and check the movement of the respective side guides are provided on the respective side guides. The positions of the respective reference stoppers are set based on information on the width of the preceding and succeeding steel sheets. The ends of the preceding and succeeding steel sheets are stopped at the specified positions on the line. The respective side guides are moved till coming into contact with the respective stoppers.