A pattern inspection apparatus includes a stage configured to mount a target workpiece to be inspected thereon, a sensor configured to include a plurality of light receiving elements arrayed in a second direction orthogonal to a first direction which moves relatively to the stage, and to capture optical images of the target workpiece by using the plurality of light receiving elements, an accumulation unit configured to accumulate each pixel data of the optical images overlappingly captured by the sensor at positions shifted each other in the second direction by a pixel unit, for each pixel, and a comparison unit configured to compare the each pixel data accumulated for each pixel with predetermined reference data.