SEAT SLIDING DEVICE AND METHOD OF MANUFACTURING THE SEAT SLIDING DEVICE

In a pair of side walls of an upper rail, a pair of right and left slits extending from lower ends of the side walls to an intermediate position are formed. Right and left side edges of at least one reinforcing plate fit into the pair of left and right slits. The upper rail includes a pair of right and left tongue pieces formed on the side walls as to be positioned higher than the slits, and the reinforcing plate includes a pair of right and left recesses formed at the upper portions of the left and right side edges and with which the pair of right and left tongue pieces are engaged. The tongue-piece enters the recess in a state where an upper end surface abuts an upper tapered surface of the recess and is bent into an S-shape in the recess and engaged with the recess.