The optical tracking system includes a marking section, an imaging section, and a processing section. The marking part includes a pattern having specific information and a 1 st lens. The 1 st and 2 nd imaging sections include 2 nd and 3 rd lenses and 1 st and 2 nd imaging units, respectively. The processing unit determines the posture of the marking unit from a 1 st coordinate conversion formula between the coordinates on the pattern surface of the pattern and the 1 st pixel coordinates on the 1 st image of the pattern and a2 nd coordinate conversion formula between the coordinates on the pattern surface of the pattern and the 2 nd pixel coordinates on the 2 nd image of the pattern including the rotation conversion between the 1 st pixel coordinates and the 2 nd pixel coordinates on the 2 nd image of the pattern, and tracks the marking unit using the determined posture of the marking unit. Thus, the marker can be accurately tracked by a simpler and easier method.