A cover mechanism of covering a hole on a casing is disclosed in the present invention. The cover mechanism includes a base, a first holder, a second holder, a cover and a resilient component. The first holder and the second holder are respectively disposed on the base. The cover is pivotably disposed on the first holder. The resilient component includes a shaft and a curved portion. The shaft pivots to the second holder. A first end of the curved portion is connected to the shaft, and a second end of the curved portion pivots to a connecting hole on the cover. The cover drives the curved portion to generate resilient deformation when rotating from a first position to a second position, and a resilient recovering force of the curved portion can be for stopping the cover at the second position.