An opening-closing device for an opening in a vehicle includes an opening-closing body for opening and closing an opening formed in a vehicle body, a hinge arm for supporting the opening-closing body in a swingable manner on the vehicle body, and a torsion bar for pressing the hinge arm in the direction in which the opening-closing body is opened. The device includes a slide rail section provided on the surface of the hinge arm, and a slider capable of sliding in the longitudinal direction of the hinge arm by being guided by the slide rail section. The slider is held in a state in which the slider is always in contact with the slide rail section in the direction in which the torsion bar presses. The torsion bar is connected to the slider.