PURPOSE: To rotate an image while displaying the image on a display screen by calculating the centroid position of a frame in accordance with an indication frame and rotating the whole frame in accordance with a mouse cursor around the centroid position.

CONSTITUTION: English letters ABCD are displayed on the display screen as the images, for example, and the frame being a rotary object is designated by the mouse cursor. The centroid position G of the frame is calculated in accordance with the designated frame, and the whole frame is rotated in accordance with the mouse cursor around the centroid position G. The frame being the rotary object can freely be set by the mouse cursor, and the whole objective frame can be displayed on the display screen by the indication of the mouse cursor around the centroid or the like after the setting. Thus, the frame can be displayed by using the mouse cursor on the display screen from the rotation of the image, and therefore rotation errors can be reduced. Thus, the movement of the image pickup system of the image and that of an image pickup object can be judged from a rotary angle.