An operation input device comprising: a substrate formed of an insulator; a plurality of detecting electrodes provided on a surface of the substrate and arranged along a longitudinal direction of the substrate; and a controller, wherein the controller is configured to detect capacitance generated between each of the plurality of detecting electrodes and an operation body when the operation body is positioned in proximity to the substrate, wherein a capacitance is defined to be a value of the capacitance at a peak of a distribution of capacitances detected by the detecting electrodes, and determine that a gesture operation by the operation body is performed when a duration from a first time when the capacitance becomes greater than or equal to a first threshold to a second time when the capacitance becomes greater than or equal to a second threshold is greater than or equal to a predetermined value, or when a length in which the operation body is moved from a first position when the capacitance becomes greater than or equal to the first threshold to a second position when the capacitance becomes greater than or equal to the second threshold is greater than or equal to a predetermined value, the first threshold being a threshold for the capacitance, wherein for each time at which the capacitance generated between each of the plurality of detecting electrodes and the operation body is detected, it is considered that the operating body exists at a position in which the capacitance is at a peak, and when a direction in the longitudinal direction in which the operation body is moved closer to the operation input device is the same as a direction in the longitudinal direction in which the operation body is moved away from the operation input device, wherein the second threshold is greater than the first threshold. a substrate formed of an insulator; a plurality of detecting electrodes provided on a surface of the substrate and arranged along a longitudinal direction of the substrate; and a controller, wherein the controller is configured to detect capacitance generated between each of the plurality of detecting electrodes and an operation body when the operation body is positioned in proximity to the substrate, wherein a capacitance is defined to be a value of the capacitance at a peak of a distribution of capacitances detected by the detecting electrodes, and determine that a gesture operation by the operation body is performed when a duration from a first time when the capacitance becomes greater than or equal to a first threshold to a second time when the capacitance becomes greater than or equal to a second threshold is greater than or equal to a predetermined value, or when a length in which the operation body is moved from a first position when the capacitance becomes greater than or equal to the first threshold to a second position when the capacitance becomes greater than or equal to the second threshold is greater than or equal to a predetermined value, the first threshold being a threshold for the capacitance, wherein for each time at which the capacitance generated between each of the plurality of detecting electrodes and the operation body is detected, it is considered that the operating body exists at a position in which the capacitance is at a peak, and when a direction in the longitudinal direction in which the operation body is moved closer to the operation input device is the same as a direction in the longitudinal direction in which the operation body is moved away from the operation input device,