A planar antenna including a substrate, multiple antenna bodies and a metal layer is provided. The antenna bodies are disposed at a surface of the substrate, and the metal layer is disposed at another surface of the substrate. The metal layer has multiple slots which interlace with the antenna bodies. The antenna bodies are partially corresponding to the metal layer and used to cooperate with a communication system which can perform a multi-path transmission to send and receive electromagnetic signals for a multiple MIMO system simultaneously.