An operation input device includes a resistance element to generate a capacitance between an operating medium and the resistance element in response to an approach of the operating medium to the resistance element, and a power source to supply electric charge to one end and the other end of the resistance element. A first electric unit measures a first electric charge transfer amount supplied to the one end of the resistance element in response to generation of the capacitance. A second unit measures a second electric charge transfer amount supplied to the other end of the resistance element in response to generation of the capacitance. A controller is connected to the first and second units, and detects a position of the operating medium in a direction perpendicular to a surface of the resistance element based on a sum of the first and second electric charge transfer amounts.