1. An image processing device, which is connected with an imaging unit for imaging an inspection object, and performs imaging processing on image data captured by the imaging unit, to make a defective/non-defective determination on the inspection object based on a result of the image processing, the device comprising: a reference image storing unit for storing a reference image to serve as a reference for a non-defective determination in association with identification information for identifying the inspection object; an image displaying unit for acquiring an image of the inspection object, to display the acquired image side by side with the reference image of corresponding identification information; an alignment unit for aligning a drawn position of the reference image and a drawn position of the acquired image; a brightness adjustment unit for performing adjustment so as to make brightness of the reference image coincide with brightness of the acquired image; and a focus adjustment unit for performing adjustment so as to make a focus on the reference image coincide with a focus on the acquired image.