An input pen of data input tablet comprising a magnetic core which is positioned at the data input tablet side end of a pen case and passes a magnetic flux generated from the data input tablet, a conductive holder for holding this core, a detection coil wound around on the core, and a lead wire led out from the coil in close contact with the holder. The magnetic flux generated by the current flowing into electrodes formed in the data input tablet is detected by the detection coil, thereby detecting a position on the data input tablet. A protective tube which covers at least the detection coil and magnetic core to protect the coil and core is also provided. An annular shield case formed of metal or other conductive material and functioning as an electromagnetic and electrostatic shield near the protective tube is provided in another embodiment.
