PURPOSE: To extend the focal depth of an image pickup device substantially in a single optical system by forming the image pickup device two-dimensionally with multiple sensors laid on a plane which is inclined in relation to the scanning direction.

CONSTITUTION: An object lens 3 is installed on the above of the X-Y taller 2 of a defective appearance inspection device and an image pickup device 4 on the above of the lens 3 with a coincidence of optical axes. The image pickup device 4 is formed by multiple one-dimensional photo-sensors 5 like CCD etc. which are composed two-dimensionally with the both ends arranged uniformly and with a parallel line up each other. The image pickup device 4 is installed in a manner that the longitudinal direction of the sensor 5 is to be parallel to the Y direction of the X-Y table 2 and the perpendicular direction of the sensor 5 is to be somewhat inclined to the X direction of the X-Y table 2. As the image pickup device 4 is formed two dimensionally with the multiple sensors 5 lined up in parallel and is inclined to the scanning X direction of a wafer 1, a clear image signal can be acquired as a whole, even when the wafer 1 is shaped by a pattern consisting of different altitudes.