There is provided a method for setting a suitable imaging magnification for each of a plurality of measurement places in a charged particle beam apparatus which images a semiconductor pattern.For a given measuring point coordinate, a line segment or a vertex representing a change in concavity and convexity near the measuring point coordinate is searched, and an imaging magnification is set so that coordinates on a sample corresponding to both ends which gives a length that serves as a reference falls in a field of view of the charged particle beam apparatus by letting a minimum distance be the reference, of distances between line segments representing a change in concavity and convexity from the measuring point coordinate or a distance between neighboring vertexes.