A method and an apparatus for calculating a scan signal so that the scan region becomes a scan region which is based on magnification ratio between desired magnification in a scan-line interval direction and desired magnification in a scan-line direction, and performing a calculation for rotating the scan direction with respect to the scan signal in order to suppress a distortion which is caused to occur when the technology where the scan direction of a charged particle beam is rotated is applied to the technology where the charged particle beam is scanned such that the scan-line interval is enlarged.