A driving mechanism for moving a vessel having a disposal box placed thereon in a front-rear direction the same as an opening/closing direction of a drawer is provided lower than a bottom surface of the vessel. A first rail extended in a movement direction of an operating unit, a second rail extended in a movement direction of the vessel provided in the drawer, and toothed pulleys for rotating a toothed belt within a horizontal plane are arranged. The first rail, the second rail, and the toothed belt are placed side by side without overlapping with each other in a vertical direction. As a result, the operation of taking out the disposal box in which used sample dispensing tips or reaction vessels are accumulated is simple.