PURPOSE: To miniaturize a guide roller mechanism by forming the device in structure in which a first roller is overlapped with the upper wall section side.

CONSTITUTION: In a roller bracket 15, a section thereof is bent and formed to an approximately crank shape, the central section of a horizontal upper wall section 15b to which a second roller 7 is supported pivotally is expanded and formed upward in an arcuate shape, and the first roller 6 supported pivotally to a vertical wall sectin 15a is arranged to the inner lower surface of the expanded section 15c. That is, since the expanded section 15c is formed, space of which the first roller can occupy when the roller 6 is disposed is extended in the direction of the expansion, and the first roller 6 is overlapped spatially with the upper wall section 15b side. Thus, a guide rail 2 can be miniaturized.