A charged particle instrument including a controlling and operating unit for controlling a charged particle source, deflecting means, and focus changing means and making a data for an image by an electric signal detected by a detector, and a recording unit for preserving a correction coefficient registered at each image-acquisition, in which the controlling and operating unit acquires plural images while changing a focus, and controls an optical condition such that a landing angle of a charged particle beam becomes perpendicular when an image for measurement is acquired on the basis of a position shift amount of a mark in the image and a correction coefficient registered to the recording unit.