1. An information processing method for obtaining placement information of a first position and orientation sensor attached to an object with respect to the object, the information processing method comprising: an image input step of inputting an image of the object captured by an image capturing device; a sensor measurement value input step of inputting a first measurement value of the first position and orientation sensor and a second measurement value of a second position and orientation sensor attached to the image capturing device; an index detecting step of detecting information about image coordinates of an index attached to the object from the image; and a placement information calculating step of calculating the placement information by using the first and second measurement values input in the sensor measurement value input step and the information about the image coordinates of the index detected in the index detecting step.