To improve detecting sensitivity by setting different thresholds for each region in response to the magnitude of noise for respective regions of an object to be inspected and thereby enabling correspondence to a variation on a surface state.

The inspecting method and a device therefor include a function to set inspection thresholds for each region and a function to set inspection thresholds for each of a plurality of detectors with an independent space. The magnitude of the noise from the object to be inspected differs from a spatial direction even if located in the same region. With maximization of the SN ratio of a detection signal by optimal signal operating process corresponding to noise from the object for each detector and region of the object, and setting of optimal thresholds, detection sensitivity can be maximized.