It is facilitated in a scanning electron microscope to save the labor of executing the reproduction test, conduct basic analysis on a problem caused in execution of the automatic observation process, and confirm details resulting in the error. Upon detecting an error from an abnormality, the scanning electron microscope extracts a sample image Im(t2) obtained by retroceding from a sample image Im(te) stored so as to be associated with time te of error occurrence by a predetermined video quantity (for example, total recording time period t2) previously set and registered by an input-output device, from sample images stored in a recording device while being overwritten, and stores a resultant sample image in another recording device.