A MOS transistor includes a gate electrode formed in a grid pattern, source regions and drain regions each surrounded by the gate electrode, and a source metal wiring connected to the source regions via source contacts and a drain metal wiring connected to the drain regions via drain contacts. The wide door panel and the narrow door panels are arranged in line so as to be slidable in the width direction such that an opening portion is opened and closed, and the opening width has a length suitable for the length of the largest workpiece on one pallet. An inlet end of the tubing is located with the rocks and sediments to be moved, which are sucked into the tubing and blown out of the opposite end of the tubing.