A key operation detection unit of an electronic keyboard instrument that suppresses increase in reaction forces with key depression operation, to improve a key touch feeling. A depression operation of any one of keys of the keyboard instrument is detected by first and second corresponding detectors of the detection unit. The detectors are surrounded by an outer resilient projection and each comprised of an inner resilient projection and a movable portion extending therefrom toward a base plate of the unit. With key depression, the movable portion of the first detector is in contact with the base plate and its inner resilient projection is deformed to generate a reaction force. With further key depression, the inner resilient projection of the second detector brought in contact with the base plate is deformed to generate a reaction force smaller than the reaction force from the first detector.