A position detecting device including a transparent sensor that is obtained by arranging a plurality of electrodes composed of a transparent electrically-conductive material in each of a first direction and a second direction intersecting each other and is disposed over a display device, the position detecting device configured to receive a signal for position detection for causing a position on the sensor to be detected and a signal for data detection generated according to predetermined digital data from a stylus pen, the position detecting device comprising: a differential amplification circuit that has a positive-side terminal and a negative-side terminal and is configured to amplify and output a difference in a signal generated at the positive-side terminal and the negative-side terminal; and a selecting circuit configured to select a first electrode or a first electrode group composed of a plurality of electrodes in which the first electrode is included from a plurality of the electrodes provided in the sensor and configured to connect the first electrode or the first electrode group to the positive-side terminal, the selecting circuit configured to select a second electrode or a second electrode group composed of a plurality of electrodes in which the second electrode is included and configured to connect the second electrode or the second electrode group to the negative-side terminal; characterised in that the selecting circuit is configured to select electrodes separated by a predetermined interval as the first electrode and the second electrode in a period in which an indicated position by the stylus pen is detected based on the signal for position detection, and the selecting circuit is configured to select electrodes separated by a shorter interval than the predetermined interval as the first electrode and the second electrode in a period in which the signal for data detection is detected. a differential amplification circuit that has a positive-side terminal and a negative-side terminal and is configured to amplify and output a difference in a signal generated at the positive-side terminal and the negative-side terminal; and a selecting circuit configured to select a first electrode or a first electrode group composed of a plurality of electrodes in which the first electrode is included from a plurality of the electrodes provided in the sensor and configured to connect the first electrode or the first electrode group to the positive-side terminal, the selecting circuit configured to select a second electrode or a second electrode group composed of a plurality of electrodes in which the second electrode is included and configured to connect the second electrode or the second electrode group to the negative-side terminal; characterised in that the selecting circuit is configured to select electrodes separated by a predetermined interval as the first electrode and the second electrode in a period in which an indicated position by the stylus pen is detected based on the signal for position detection, and the selecting circuit is configured to select electrodes separated by a shorter interval than the predetermined interval as the first electrode and the second electrode in a period in which the signal for data detection is detected.