A MTF measuring system includes measurement result screen data indicative of an object image and an MTF curve image are generated in accordance with the object image data obtained by photographing the object and the MTF curve image data indicative of the MTF curve generated from MTF data that become an index to evaluate lens performance. The measurement result screen based on the generated measurement result screen data is displayed on a real time basis in the case of evaluation measurement operations of the lens performance. A user can grasp the necessity for a focus adjustment from the MTF curve image on the measurement result screen. If necessary, the user can adjust the focus of the object displayed together with the MTF curve image, and at the same time can evaluate the lens performance from the MTF curve image.