A system for detecting actual position of a material handling vehicle in a warehouse in which a plurality of racks composed of upright frame members and lateral frame members connecting the upright members are installed so that material handling vehicles can travel along the passageway between the racks so that current position of the material handling vehicle in the warehouse can be detected with increased reliability even if some of the reflections fail to be received by the sensors. Reflector plates are attached to each of the upright frame members and the lateral frame members along longitudinal direction thereof, sensors are attached to the vehicle, and a controller is installed on the vehicle to estimate current location of the vehicle based on combination of the number of reflections actually received by the reflector plates and counted by the controller.