An air-conditioning vent structure includes a duct portion supported by a duct panel, the duct portion including first and second outlets formed at an upper portion thereof and separated by a partition, and a curvature portion including a curvature, a sliding door slidable along an upper portion of the curvature portion at a lower end portion of the partition, the sliding door including a hole to adjust opening widths of the first and second outlets in accordance with a degree of sliding, a driving portion connected to the sliding door at a lower end portion of the duct panel and configured to apply driving force to the sliding door so that the sliding door slides in opposite directions, and a controller electrically connected to the driving portion to perform a control operation to allow the sliding door to slide in opposite directions in accordance with a use mode.