a pattern inspection apparatus includes a light source which emits ultraviolet light , an irradiator which reduces coherency of the ultraviolet light and irradiates the coherency reduced ultraviolet light onto a specimen on which a pattern is formed through an objective lens , and a focus control means which projects light on the specimen from outside the objective lens , detects light reflected from the specimen by the projection and adjusts a height of the specimen relative to the objective lens . the apparatus further includes an image which forms an image of the specimen irradiated with the ultraviolet light and detects the formed image with a sensor , an image processor which processes a signal outputted from the sensor to detect a defect of the specimen , and a display which displays information of the defect detected by the image processor .