1. An electron microscope for directing an electron beam at a specimen supported tiltably and gaining TEM images based on electrons transmitted through the specimen, the microscope being fitted with a signal processing circuit for implementing computerized tomography according to data about the gained TEM images of the specimen, wherein said signal processing circuit performs two-dimensional correlation processing between each of a series of TEM images obtained from the specimen tilted by plural angles and a reference image to thereby select and extract an identical field of view, whereby correcting positional deviation of the specimen.