A detachable cover module includes a bezel body, a button, and a sliding member. The button is pivotally connected to the bezel body. The button includes a pushing member. The sliding member includes a connecting portion and a guiding element. When the button is pressed in a first direction, the pushing member pushes the guiding element, so that the connecting portion moves from a position protruding outward from the bezel body toward a position not protruding outward from the bezel body. When the button is not pressed, the connecting portion of the sliding member is normally maintained at the position protruding outward from the bezel body. The detachable cover module is adapted to be pivotally connected to a body of a chassis to selectively expose or cover an opening of the chassis body.