An operation input device, comprising: a resistance element; a power source unit (131, 132) configured to supply electric charge to one end and the other end of the resistance element; a first electric charge amount measuring unit configured to measure an electric charge amount supplied to the one end of the resistance element; a second electric charge amount measuring unit configured to measure an electric charge amount supplied to the other end of the resistance element; and a controller connected to the first electric charge amount measuring unit and the second electric charge amount measuring unit, in approaching an operating medium to the resistance element, a capacitance is generated between the resistance element and the operating medium, and a position of the operating medium is detected based on a moving electric charge amount measured in the first electric charge amount measuring unit and the second electric charge amount measuring unit, wherein the position of the operating medium in a direction perpendicular to a surface of the resistance element is detected based on a sum of the moving electric charge amount measured in the first electric charge amount measuring unit and the second electric charge amount measuring unit, and wherein a position of the operating medium in a direction parallel to the surface of the resistance element is detected based on a value of the moving electric charge amount measured in the first electric charge amount measuring unit with respect to the sum of the moving electric charge amount or on a value of the moving electric charge amount measured in the second electric charge amount measuring unit with respect to the sum of the moving electric charge amount. a resistance element; a power source unit (131, 132) configured to supply electric charge to one end and the other end of the resistance element; a first electric charge amount measuring unit configured to measure an electric charge amount supplied to the one end of the resistance element; a second electric charge amount measuring unit configured to measure an electric charge amount supplied to the other end of the resistance element; and a controller connected to the first electric charge amount measuring unit and the second electric charge amount measuring unit, in approaching an operating medium to the resistance element, a capacitance is generated between the resistance element and the operating medium, and a position of the operating medium is detected based on a moving electric charge amount measured in the first electric charge amount measuring unit and the second electric charge amount measuring unit, wherein the position of the operating medium in a direction perpendicular to a surface of the resistance element is detected based on a sum of the moving electric charge amount measured in the first electric charge amount measuring unit and the second electric charge amount measuring unit, and wherein a position of the operating medium in a direction parallel to the surface of the resistance element is detected based on a value of the moving electric charge amount measured in the first electric charge amount measuring unit with respect to the sum of the moving electric charge amount or on a value of the moving electric charge amount measured in the second electric charge amount measuring unit with respect to the sum of the moving electric charge amount.