PURPOSE: To improve accuracy for positioning by deriving a height, where noise outputted from an antenna is the strongest, and stopping the antenna at that position while elevating the antenna by a means to elevate the antenna.

CONSTITUTION: The noise outputted from a spectrum analyzer 16 is inputted through an input interface 14 to an antenna elevating device 11 while elevating 11 the antenna. For the inputted noise signal, the level is discriminated by a signal conversion circuit 15, the height with the highest level is calculated, and an antenna elevating signal is outputted to an elevation control circuit 13. The antenna elevator 12 is controlled to be automatically stopped at the position where the level is the highest. An operator 17 can also manually control the elevation control circuit 13. Thus, the optimum height of the antenna is automatically selected with high accuracy.