The present invention provides a key structure, including: a key cap, a support board, an elastic element, and a support element. The elastic element includes an elastomer and an elastic piece. The elastomer has a first surface and a second surface, where the first surface includes a first protrusion portion and a second protrusion portion. The support element is connected the key cap and the support board and surrounds the elastic element. When the key cap descends, the first protrusion portion is pressed by the key cap and generates a deformation, so as to form a first pressing stroke, and subsequently, the key cap presses the second protrusion portion to enable the elastic piece to generate a deformation, so as to form a second pressing stroke.