The present disclosure provides a wafer inspection technology that involves less degradation of the image quality even when an object to be observed has a variation in height due to warpage, etc. of a wafer. This wafer inspection apparatus obtains an image with less degradation by: adjusting the focal point of an observation optical system to a height measured by a height sensor for measuring wafer surface heights; and further, correcting a switching signal for a CCD line sensor on the basis of stage position data and optical magnification data corresponding to the height so as to make a correction corresponding to the wafer surface height.