A leading-edge high-lift device according to an embodiment of the present invention is a leading-edge high-lift device that is deployable and retractable from/into a fixed leading edge of a main wing of an aircraft and includes: a leading edge portion; a trailing edge portion that forms a gap between a trailing edge portion and the main wing during deployment; a cusp portion formed at a lower edge of the leading edge portion; a lower surface portion formed between the cusp portion and the trailing edge portion; and a curved hump portion that is locally provided on a surface of the lower surface portion and protrudes toward the main wing in a cross-sectional shape perpendicular to a wing span direction of the main wing.