An information processing method includes the steps of acquiring a sense image of an image sensing unit, acquiring coordinate values of registered indices, detecting image positions of the registered indices in the sense image, and calculating position and orientation of the image sensing unit on the basis of the detected image positions of the registered indices and the coordinate values of the registered indices. Additional steps include detecting an image position of an additional index in the sense image in accordance with a user's instruction, calculating a coordinate value of the additional index using the image positions of the registered indices, the coordinate values of the registered indices, the position and orientation of the image sensing unit, and the image position of the additional index, and registering the calculated coordinate value of the additional index as a registered index.