A method is provided for estimating the placement information of a plurality of types of markers of which the amounts of the placement information differ respectively, detects a plurality of types of markers from multiple images, calculates the position where the detected marker is projected on an image surface based on the approximate values of the positions and orientations of an imaging device when multiple images are photographed, obtains the correction value of the placement information of a marker so as to reduce a sum of error between the position of the detected marker on the image surface and the projected position of the marker calculated, corrects the placement information of the marker, and also calculates the placement information of a plurality of types of markers by repeating these processes.