An electronic device includes a frame, a covering structure and a functional module. The frame has an opening and a fixing portion corresponding to the opening. The covering structure and the functional module constitutes a function expansion assembly. The covering structure is used to be detachably fixed at the electronic device and to cover the opening. The functional module includes an expansion circuit board and an operation interface. The expansion circuit board is used to be detachably fixed at the fixing portion, and the operation interface is located corresponding in position to the opening. When the covering structure is detached from the electronic device, the operation interface is accessible through the opening.