A plate material conveyance apparatus adapted to be disposed next to a plate processing machine, which apparatus comprises: an unprocessed plate material placement unit; a processed plate material placement unit disposed at a position different from that of the unprocessed plate material placement unit; a temporary placement table slidable between the unprocessed plate material placement unit and the processed plate material placement unit and having a position switching capability to an upper position above each above the placement units (12, 13); a loader reciprocally movable between the unprocessed plate material placement unit and the plate processing machine and operable to load an unprocessed plate material onto the plate processing machine; and an unloader reciprocally movable between the unprocessed plate material placement unit and the plate processing machine at a location below a region of travel of the loader and in parallel to the loader, the unloader being operable to unload a processed plate material from the plate processing machine onto the temporary placement table then assuming a position above the unprocessed plate material placement unit; characterized in that the temporary placement table is adapted to transfer the processed plate material, which has been received from the unloader at an upper position of the unprocessed plate material placement unit, onto the processed plate material placement unit, the apparatus further comprising a motion constraining member to constrain the processed plate material, which has been transported to the processed plate material placement unit while having been mounted on the temporary placement table, from moving in a direction where the unprocessed plate material placement unit exists, wherein as the temporary placement table returns to the unprocessed plate material placement unit in a condition with the movement of the processed plate material constrained by the motion constraining member, the processed plate material is permitted to be mounted on the processed plate material placement unit. an unprocessed plate material placement unit; a processed plate material placement unit disposed at a position different from that of the unprocessed plate material placement unit; a temporary placement table slidable between the unprocessed plate material placement unit and the processed plate material placement unit and having a position switching capability to an upper position above each above the placement units (12, 13); a loader reciprocally movable between the unprocessed plate material placement unit and the plate processing machine and operable to load an unprocessed plate material onto the plate processing machine; and an unloader reciprocally movable between the unprocessed plate material placement unit and the plate processing machine at a location below a region of travel of the loader and in parallel to the loader, the unloader being operable to unload a processed plate material from the plate processing machine onto the temporary placement table then assuming a position above the unprocessed plate material placement unit; characterized in that the temporary placement table is adapted to transfer the processed plate material, which has been received from the unloader at an upper position of the unprocessed plate material placement unit, onto the processed plate material placement unit, the apparatus further comprising a motion constraining member to constrain the processed plate material, which has been transported to the processed plate material placement unit while having been mounted on the temporary placement table, from moving in a direction where the unprocessed plate material placement unit exists, wherein as the temporary placement table returns to the unprocessed plate material placement unit in a condition with the movement of the processed plate material constrained by the motion constraining member, the processed plate material is permitted to be mounted on the processed plate material placement unit.