Provided are a device and a method allowing a crystal orientation to be adjusted with adequate throughput and high precision to observe a sample, regardless of the type of the sample or the crystal orientation. In the present invention, the method comprises: setting a fitting circular pattern (26) displayed overlaid so that a main spot (23) is positioned on the circumference thereof, on the basis of the diffraction spot brightness distribution in an electron diffraction pattern (22b) displayed on a display unit (13); setting a vector (28) displayed with the starting point at the center position (27) of the displayed circular pattern (26), and the end point at the location of the main spot (23) positioned on the circumference of the circular pattern (26); and adjusting the crystal orientation on the basis of the orientation and the magnitude of the displayed vector (28).