A position and orientation estimating method and apparatus are disclosed in which position and orientation measured values are acquired from an image pickup device, and in which an index is detected from an image of a real space photographed by the image pickup device, and identified. By using the index obtained, correction values for correcting position and orientation measured values are calculated. Correction values at a current time are calculated using the calculated corrected values together with correction values for past n-times. The obtained correction values at the current time are stored and accumulated, and the position and orientation measured values are corrected by the correction values at the current time. If the detection or identification of the index ends in failure, the position and orientation measured values are corrected by using correction values obtained in the past.