A method and apparatus for efficiently executing two types of measurements with an optical measuring device and a scanning electron microscope are provided. For example, the method and apparatus may execute the following steps: calculating an average of the dimensional values of a plurality of scanned feature objects; and calculating an offset of a dimensional value on the basis of a difference between the calculated average value and the dimensional value of the feature object obtained when the light is irradiated. The offset between measurement values between the optical measuring device and the scanning electron microscope can be determined precisely.