To solve brake action when opening/closing a sliding door 1 caused by the dislocation of guide rollers by positively engaging the guide rollers of V-shaped arrangement installed at a slide box, with a guide rail of V-shaped cross section in a non-rail sliding door.

A plurality of lower guide rollers are fixed into the fixed positions of the slide box. In the placed state of the sliding door 1, a plurality of upper guide rollers 4a are adjusted to pressure-hold the sliding door 1, and the adjustment is made by rotationally operating a bolt 5 to guide the guide rollers 4a in an inclined manner by a bracket 3 fixed to the slide box and to move the guide rollers 4a horizontally downward so as to be positively engaged with the guide rail 11. The sliding door 1 is thereby pressure-held without dislocation.