A back cover includes a metal body having a first side, a second side, and a groove that is formed at the first side. The metal body further has a first radiator, a second radiator, and a ground radiator. The first radiator is disposed in the groove, and has a main portion and a support portion that cooperatively form a T-shape. The main portion includes a feeding end adjacent to a closed end of the groove. The second radiator is adjacently connected to the groove and is defined by the first and second sides, and an edge of the groove. The ground radiator is formed by a portion of the metal body excluding the first and second radiators. The second radiator and the support portion are connected to the ground radiator. The first and second radiators, and the ground radiator are serve as an antenna structure.