A semiconductor-processing apparatus includes: a wafer handling chamber; a wafer processing chamber; a wafer handling device; a first photosensor disposed in the wafer handling chamber in front of the wafer processing chamber at a position where the wafer partially blocks light received by the first photosensor at a ready-to-load position and substantially entirely blocks light received by the first photosensor when the wafer moves from the ready-to-load position toward the wafer processing chamber in the x-axis direction; and a second photosensor disposed in the wafer handling chamber in front of the wafer processing chamber at a position where the wafer does not block light received by the second photosensor at the ready-to-load position and partially blocks light received by the second photosensor when the wafer moves from the ready-to-load position toward the wafer processing chamber in the x-axis direction.