A marker placement information estimating method includes a constraint condition setting step for setting a constraint condition that can be defined with a geometric condition regarding placement information of markers, a capturing step for capturing photographed images including a marker image, a marker detecting step for detecting markers from the photographed images, and an estimating step for estimating the placement information of the markers using the positions of the detected markers on the images and the constraint condition. Thus, even if a constraint condition regarding the placement of markers exists, the placement information can be obtained with precision so as to satisfy the constraint condition.