A pattern measuring device ensures highly accurately measuring a depth and a three-dimensional shape irrespective of a formation accuracy of a deep trench and/or a deep hole. Therefore, in the present invention, the measuring system detects backscattered electrons from a pattern caused by an irradiation, compares backscattered electron signal intensities from a top surface, a bottom surface, and a sidewall of the pattern, and calculates a three-dimensional shape (or height information) of the sidewall based on a difference in heights of the top surface and the lower surface. The measuring system compares the calculated three-dimensional shape of the sidewall with a three-dimensional shape of the sidewall estimated based on an intensity distribution (open angle) of a primary electron beam, corrects the estimated three-dimensional shape of the sidewall based on a difference in the comparison, and corrects until the difference in the comparison becomes an acceptable value.