In a method of estimating a camera attitude, based on the past-detected position of a marker and an appropriate camera attitude provided during current frame imaging, the position of the maker to the current frame is approximately predicted. Through extraction of points which are near the predicted marker position (marker neighboring points), a group of points are obtained. An attitude of the camera (rotation matrix and translation matrix) which optimizes an estimation function is obtained for re-estimating the camera attitude, where the estimation function needs, as its condition, a distance between the marker neighboring points included in the point groups and an estimation plane on which the marker is positioned. The point groups include many points extracted from the neighborhood of the marker, so that the preliminarily estimated approximate camera attitude can be corrected and estimated with higher accuracy even in an environment with occlusion.