A detector detects at least one of environmental information on the environment and physical information on the user's physical condition, when the user gets into a vehicle. Each of the environment and the physical condition is divided into a plurality of zones. A memory stores statistical data each representing the probability of the user selecting one of the driving positions in the vehicle in one of the zones. One of the driving positions can, from the probabilities allotted to them, be estimated to be optimum for the user in the zone into which the detected information falls. As a result, even if the user's preference in driving position changes with the environment or the user's physical condition in which the user gets into the vehicle, it is possible to adjust the driving position automatically according to the current preference.