A plate material processing system includes a plate material processing machine and a loader. The plate material processing machine holds a front end portion of an unprocessed plate material by a work holder and moves the unprocessed plate material on a table forward, backward, leftward and rightward. The loader includes: a plate material attaching unit; and a pivoting mechanism for pivoting the plate material attaching unit on a predefined arc-shaped trajectory while maintaining the plate material attaching unit in a constant orientation as viewed in a planar manner. When the plate material attaching unit is at a foremost position, the work holder is positioned to the other side of the left and right sides relative to a processing head, away from the unprocessed plate material loading position side, thereby preventing the work holder and the plate material attaching unit from interfering with each other.
