PROBLEM TO BE SOLVED: To provide a system capable of accurately measuring a position attitude of a marker even when the marker and an observation object of the marker face each other.SOLUTION: In a position attitude detection system including a marker using a micro-lens array, a camera which photographs the marker and a computer, the marker includes: a lens area constituted such that a moire pattern is generated by a micro-lens array and a mark column in which a plurality of marks are arrayed analogous to pitches between a plurality of lens constituting the micro-lens array and four reference points, and the position attitude of the marker is determined on the basis of the four reference points, and the moire pattern is analyzed to calculate an angle made by a straight line connecting the center of an integrated mark which appears in the lens array by the moire pattern and the observation point of the marker with the marker, and the position attitude of the marker is corrected by using the calculated angle.