A method of detecting a position on a touchscreen panel including a first resistive film having first and second electrodes provided at its corresponding ends in a first direction and a second resistive film having third and fourth electrodes provided at its corresponding ends in a second direction perpendicular to the first direction includes measuring a potential at the first electrode with supply voltage applied to a first resistor connected to the first electrode with the second electrode grounded; measuring a potential at the third electrode with the supply voltage applied to a second resistor connected to the third electrode with the fourth electrode grounded; measuring potentials at the third and fourth electrodes with the supply voltage applied to the first electrode with the second electrode grounded; and measuring potentials at the first and second electrodes with the supply voltage applied to the third electrode with the fourth electrode grounded.