A packet processing method adapted to a software-defined network is provided. The packet processing method includes the following steps: receiving an upstream packet transmitted to a remote network from a user equipment; removing a tunnel header of the upstream packet, and transmitting the upstream packet to the remote network; receiving a downstream packet transmitted to the user equipment from the remote network; selecting one of a plurality of routing paths coupled to the user equipment to transmit the downstream packet; and adding a tunnel header corresponding to the selected routing path to the downstream packet, and transmitting the downstream packet to the user equipment through the selected routing path.
