An inspection object is supported by a table. Light is emitted from a light source to illuminate the inspection object. An optical unit illuminates the inspection object with light, wherein the light is transmitted through the inspection object. Another optical unit illuminates the inspection object with light, wherein the light is reflected by the inspection object. Light transmitted through the inspection object is incident to a first sensor. Light reflected by the inspection object is incident to a second sensor. A defect of a pattern of the inspection object is detected using optical image data output from at least one of the sensors. A line width error is obtained by comparing line widths obtained from design data and optical image data of the pattern. A polarized beam splitter is disposed, movable between the inspection object and the first sensor, and between the inspection object and the second sensor.