A pattern inspection apparatus includes a light source, a stage configured to mount thereon a substrate with a pattern formed thereon, a first laser measuring unit configured to measure a position of the stage by using a laser beam, a sensor configured to capture a pattern image obtained from the pattern, formed on the substrate, irradiated by light from the light source, an optical system configured to focus the pattern image on the sensor, a second laser measuring unit configured to measure a position of the optical system by using a laser beam, a correction unit configured to correct a captured pattern image by using a difference between the position of the stage and the position of the optical system, and an inspection unit configured to inspect whether there is a defect of the pattern by using a corrected pattern image.