A laser interferometer that includes a laser interferometer, an position sensitive detector detecting an offset of an optical axis of the laser interferometer, a biaxial rotator turning the laser interferometer toward an arbitrary direction, an angle sensor detecting a rotation angle of the biaxial rotator, a retro reflector reflecting reflected light in a direction parallel to incident light, and a controller performing feedback control of the biaxial rotator so as to track the retro reflector based on signals from the position sensitive detector and the angle sensor. The tracking-type laser interferometer starts tracking control when return light from the retro reflector is returned to a detection range of the position sensitive detector, and changes gain for the feedback control in accordance with a behavior for a position of the return light on the position sensitive detector due to the tracking control.