Abstract: The present invention is an orientation flat aligner for preventing the angle deviation of the flat edge of the wafer. This invention applies two new designs to the aligner: (1) The two parallel rollers with different radius instead of two parallel rollers the same radii prevent the problem of the angle deviation to line up the flat edge of the wafer. (2) placing the photosensor on the orientation flat aligner instead of on the sensor bracket avoids the detection error because of the photosensor position relate to the orientation flat aligner position and saves time on checking whether the flat edge of the wafer line up or not.