Abstract: A portable electronic device includes a computer housing and a cover, wherein the computer housing includes a housing side portion and a housing surface portion neighboring to the housing side portion, an accommodating recess, a pivot slide recess, and a hook slide recess. The cover includes a cover body, a pivoting portion and a hook portion. The housing side portion and the housing surface portion are recessed together so as to define the accommodating recess. The accommodating recess is provided with two positioning areas and a socket area in connection with the two positioning areas, and that the socket area is provided with an extension socket. The cover body covers, selectively, the accommodating recess, and that the pivoting portion can slide and can be pivotally arranged in the pivot slide recess, while the hook portion can slide and can be arranged in the hook slide recess.