Disclosed is a scanning transmission type electron microscope provided with a scanning transmission electron microscope provided with an aberration corrector 805 for correcting the aberration of an electron-optical system that irradiates electron beams to a sample (808); a bright field image detector (813) for detecting electron beams that have transmitted through the sample; a camera (814); and an information processing apparatus (703) for processing signals detected by the detectors. The information processing apparatus divides a Ronchigram obtained by the detectors into a plurality of areas, and calculates a feature vector (W; 903), which reflects the magnitude and direction of an on-axis secondary comma aberration (B2), from the values of an off-axis defocus {C1(τ)} to be obtained for each of the plurality of areas, and the distance (τ) from the center of the Ronchigram to the center of the plurality of areas, and also calculates the correcting condition for the on-axis secondary comma aberration with the feature vector. In such a way, a scanning transmission type electron microscope that can correct he on-axis secondary comma aberration thereof in a short period of time, and efficiently, was able to be provided.