A communication device including a supporting plate and an antenna system is provided. The supporting plate includes a conductive plate and a non-conductive plate. The conductive plate has a first edge and a second edge. The antenna system includes at least two antennas, which are both disposed at the first edge of the conductive plate and operate in at least a first band. A distance between the first edge and the second edge of the conductive plate is about 0.25 wavelength of the lowest frequency in the first band, and the distance is smaller than a length of the first edge.