It is difficult for a material having low resistance to electron beam irradiation to obtain an electron microscopic image having a high S/N ratio. A conventional image smoothing process can improve stability of measurement, but this process has a problem of measurement errors for absolute values, reduction of sensitivity, deterioration of quality of cubic shape information and the like. In the present invention, by performing an image averaging process without deteriorating cubic shape information of a signal waveform in consideration of dimension deviation of a measurement target pattern, measurement stability is compatible with improvement of precision and sensitivity. Accordingly, it is possible to realize measurement of pattern dimensions and shapes with high precision and control of a highly sensitive semiconductor manufacturing process using the measurement.