An image processing device is provided that can precisely measure the photographing position or posture of a photographing device or the coordinates of an object based on sequentially changing photographed images. A series of sequentially photographed images are acquired, from which feature points are extracted. The feature points are tracked and correlated. Stereo images are selected from the series of photographed images correlated. Images selectable as stereo images are grouped into a group of images, from which stereo images are selected, before an orientation and a 3D measurement are performed. The images are grouped according to the distance from the object to the photographing position or the photographing magnification. Images with abrupt changes are removed so as to improve the measurement precision.