A coordinate detecting device includes a resistive film disposed on a quadrangular substrate; a power source for applying a voltage to the resistive film; four electrodes connected to the power source and disposed in four corners of the resistive film; four switches each disposed between the power source and a corresponding electrode; four ammeters for measuring currents flowing through corresponding electrodes; and a grounded conductive film for detecting coordinates of a contact point on the resistive film when the conductive film is brought in contact with the resistive film. The voltage is applied sequentially to the electrodes by opening and closing the switches. When the conductive film is brought in contact with the resistive film, the ammeters sequentially measure currents flowing through the corresponding electrodes. The coordinates of the contact point are detected based on positions of the electrodes and resistances obtained using the measured currents.