The present disclosure provides an optical tracking system for tracking a location and a posture of a marker. The marker is attachable to a target and configured so that a pattern surface formed inside the marker is visible through an optical system formed in an aperture. The system includes a processor configured to determine the posture of the marker based on a first image in which a part of the pattern surface viewed through the aperture is captured at an infinite focal length, and to determine the location of the marker based on a second image and a third image in which outgoing lights emitted through the aperture in different directions are captured at a focal length shorter than the infinite focal length.