A measurement line segment projection unit (400) projects, onto a sensed image, a three-dimensional model which is arranged at the position and orientation of a physical object (199). A search range is set for each side of the virtual object projected onto the sensed image, near the side of the virtual object in the sensed image based on a positional relationship between the side and other sides of the virtual object. A side of the physical object (199) on the sensed image is searched for within the search range for each side of the virtual object. The position and orientation relationship between the physical object (199) and an image sensing device (50) is calculated using the correspondence relationship, determined based on the search result, between each side of the three-dimensional model projected onto the sensed image and each side of the physical object (199) located on the sensed image.