Provided is a pattern defect inspecting apparatus wherein inspection performance is stabilized. The defect inspecting apparatus, which has a plurality of configuration units and inspects defects on the surface of a sample, is provided with a means for monitoring time-dependent changes and failures of some of or all of the configuration units, and a means for notifying the user of the results of the monitoring. Furthermore, a unit which can perform correction is provided with a correcting means, and also a means for replacing a failure component with a spare component which has been prepared in the device.