Line-edge roughness or line width roughness is evaluated while preventing influence of noise caused by a device or an environment. Therefore, an averaged signal profile 405 in which a moving average of S pixels (S is an integer greater than 1) is taken in a Y direction is obtained from a signal profile showing a secondary electron signal amount distribution in an X direction with respect to a predetermined Y coordinate obtained from a top-down image, an edge position 406 of a line pattern is extracted based on the averaged signal profile, and a noise floor height is calculated based on a first power spectral density 407 of LER data or LWR data based on the extracted edge position and a second power spectral density 409 of a rectangular window function corresponding to the moving average of the S pixels.