A position and an orientation of an image capturing device or an object to which an inclination sensor is mounted are obtained without performing iterative calculation. A position and orientation measuring method includes the steps of: inputting a measured inclination value of an inclination sensor mounted to one of an object and an image capturing device; inputting a captured image from the imagecapturing device; detecting an index on the object from the captured image; and calculating a position and an orientation of one of the object and the image capturing device to which the inclinationsensor is mounted on the basis of the measured inclination value, an image coordinate of the detected index, and already-known positional information on the detected index without performing iterativecalculation.