PURPOSE: To perform electron beam scanning in an electron beam scanning region with no irregularity by making the X-direction scanning signal and the Y-direction scanning signal asynchronous and repeatedly scanning a sample when the average analysis mode is selected.

CONSTITUTION: When the analysis mode to obtain the average information is specified, a switch S1 and a switch S2 are first connected to the contact (b) side, and the connection between a Y-direction scanning signal generator 4y and a synchronization circuit 7 is cut off. The scanning signal generated by the Y-direction scanning signal generator 4y and the scanning signal generated by an X-direction scanning signal generator 4x are fed to deflectors 2x and 2y in the asynchronous state. When the X-direction scanning signal and the Y-direction scanning signal are in the asynchronous state, the loci of the scanned electron beams are not overlapped even if the scanning is repeated, and the region on the sample surface can be scanned with no irregularity.