An operation input device includes a knob for operations, disposed in a display region of a touch display; a plurality of conductor columns provided in the knob; a touch point detecting unit that detects a touch point corresponding to at least one of the plurality of conductor columns; a location determining unit that determines a location of at least one of the plurality of conductor columns, using a result of the detection by the touch point detecting unit; and a location estimating unit that estimates, when there is a conductor column that has not been detected as a touch point by the touch point detecting unit, a location of the conductor column that has not been detected as a touch point by the touch point detecting unit, using positional relationship information indicating a positional relationship between the plurality of conductor columns in the knob and location history information indicating a history of locations of the respective plurality of conductor columns.