An imaging apparatus index detecting unit detects an index in a physical space from an image captured by an imaging apparatus including a first camera. A position and orientation estimating unit estimates the position and orientation of the imaging apparatus based on information relating to image coordinates of a detected index. A second camera index candidate detecting unit monitors an index on the imaging apparatus with a second camera positioned in the physical space, and detects an index candidate. A position constraint condition calculating unit calculates a position constraint condition based on information relating to image coordinates of a detected index candidate. A second camera index identifying unit identifies a second camera index based on the estimated position and orientation of the imaging apparatus and the position constraint condition of the second camera index candidate.