A frame body of the metal middle frame includes a first side and a second side, which are jointed at a side edge of the first side and second side; an L-shaped slit is arranged on the frame body, and includes a first slit edge and a second slit edge which are jointed at an end point of the first slit edge and the second slit edge, the first slit edge is arranged on the first side, and the second slit edge is arranged on the second side; and a millimeter-wave antenna is arranged in the L-shaped slit, and the millimeter-wave antenna is configured to perform millimeter-wave radiation through the first slit edge and the second slit edge.