Approaching a farm implement to perform a hitching maneuver is an important task in agricultural automation. Such as, approach to an object requires a robust positioning method. This study aimed to develop a positioning method for an autonomous tractor to approach an implement in the field using an outdoor Laser Range Finder (LRF). Navigation performance based on localization of reflectors by the LRF was examined using an actual-size autonomous tractor. First, the accuracy of LRF positioning using flat reflectors was tested. The positioning errors of the flat reflectors were less than 5cm up to 15m distance from the LRF. Second, field experiments were carried out in which the autonomous tractor approached the implement on a concrete surface and a field covered with grasses. The results of the field experiments showed that the autonomous tractor could approach to the implement's position within a final lateral error of 1cm and directional error of 1°, for the single reflector positioning method, both on the concrete surface and on the field covered with grasses. In the two-reflector positioning method, approaching the implement was done within a lateral error of 1cm for the concrete surface and 2cm for the field covered with grasses; the directional error was less than 1° for both surfaces. These results confirmed that positioning with reflectors as artificial landmarks for an LRF enabled navigation of the vehicle to the implement's position with high accuracy.