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.