PURPOSE: To install an input device of position information of the information process system at an easy-to-use position for the free use, by installing a loop-shaped antenna at both sides of a tablet respectively.

CONSTITUTION: Receiving loop-shaped antennas 30 and 31 are set at the right and left sides of a tablet 12. When an indication pen 23 is on one board face of the tablet 12, the reception signals of both antennas 30 and 31 produced by the radiated electric waves are added to each other to be supplied to a receiving part 36. In case the pen 23 goes beyond the antenna 30 or 31 and at a position outside the tablet 12, the reception signals of both antennas are offset to each other with the reverse phase. As a result, the signals to be supplied to the part 36 is extremely attenuated to be substantially O in case the space between the pen 23 and the tablet 12 is large enough compared with the space between the antennas 30 and 31. Accordingly no distrubance is given from other devices.