A hard disk device includes a main portion and two pads. The main portion includes a front end, a rear end, a first side surface, a second side surface and a bottom surface. The first side surface defines a first connecting hole near the front end. The second side surface defines a second connecting hole near the front end. The bottom surface defines a first bottom connecting hole corresponding to the first connecting hole and a second bottom connecting hole corresponding to the second connecting hole. Each pad includes two connecting poles. A distal end of each connecting pole is toward the other connecting pole. The connecting poles of one of the pads are respectively insert into the first connecting hole and the first bottom connecting hole, and the connecting poles of the other pad are respectively insert into the second connecting hole and the second bottom connecting hole.