Electron microscope

An electron microscope which permits an operator to perform astigmatic correction and beam alignment. A field of view capable of clearly displaying astigmatism or beam misalignment in terms of a Ronchigram is placed on the optical axis. Then, the operator selects a Ronchigram display mode. A first or second TV camera such as a CCD camera is selected and placed on the optical axis while maintaining the electron optics in the STEM imaging mode. Under this condition, a Ronchigram signal is obtained from the TV camera and supplied to a computer via a TV power supply and an interface. As a result, a Ronchigram of appropriate size and brightness is displayed in an image display region on a display device. The operator corrects astigmatism or adjusts the alignment while observing the Ronchigram.