To improve the handwriting precision of characters, etc., by reproducing a pen-inputted trace from detected coordinate values and arranging it on the coordinate system on a liquid crystal panel.

When a pen tip 11 is in contact with a display device board surface 12 and a switch part 23 is in an OFF area, the device is OFF. The pen tip 11 is in contact with the display device board surface 12 and pressure is applied to the pen tip 11, a switch part 23 has reached an ON area, so an ON signal is sent from the detection pen, which turns ON. When a position is indicated on a liquid crystal panel by using the detection pen 10 equipped at the tip with a detection electrode which detects a scanning signal applied to an electrode in a period wherein a sequential scan panel of level at which the liquid crystal does not respond is applied to the electrode, the indicated coordinates are found from the time when the potential obtained from the detection pen 10 becomes maximum and the pen-inputted trace is reproduced from the coordinate values and arranged on the coordinate system on the liquid crystal panel.