An unauthorized use preventing device includes: a first measuring unit that measures a global position thereof and outputs the global position as first position information; and a first transmission unit that wirelessly transmits the first position information to an outside. The security section includes: a second measuring unit that measures a global position thereof and outputs the global position as second position information; a first receiving unit that receives the first position information; a position comparison unit that determines whether an inter-instrument distance calculated based on the first and second position information is less than a threshold distance or equal to or more than the threshold distance, and outputs a result of the determination as a position comparison result signal; and a logical product calculation unit that calculates and outputs a logical product of the position comparison result signal and a power supply turning-on signal.