A button includes a base, a plurality of restricting members, a cap and a linking member. The base includes two positioning holes disposed on two sides of the base, respectively. Each of the restricting members includes an engaging portion, and the engaging portions are disposed corresponding to the positioning holes, respectively. The cap is disposed opposite to the base and connected with the restricting members. The linking member is disposed on the base, two ends of which are connected with the engaging portions, respectively. The engaging portions drive the linking member to rotate and are respectively inserted into the positioning holes when the cap moves toward a direction of the base. A keyboard device including the button is also disclosed.