An antenna structure includes a metal frame. The metal frame includes a first gap, a second gap, a third gap, and a fourth gap to separate a first antenna, a second antenna, a third antenna, and a fourth antenna from the metal frame. The metal frame includes a fifth antenna. The first antenna, the second antenna, the third antenna, and the fourth antenna cooperatively form a first multiple-input multiple-output (MIMO) antenna to provide a 4×4 multiple-input multiple-output function in a second frequency band. The first antenna, the second antenna, the third antenna, and the fifth antenna cooperatively form a second MIMO antenna to provide a 4×4 multiple-input multiple-output function in a third frequency band. The first antenna and the third antenna cooperatively form a third MIMO antenna to provide a 2×2 multiple-input multiple-output function in a first frequency band.