To obtain a packet transmission method which reduces transfer delay of a packet which requires real time property, and enables effective transmission.

In the communication system, wired networks are connected for wireless communication via a wireless access control device connected to each thereof. A communication device is provided between the wired network and the wireless access control device. A communication device connected to the wireless access control device at a sending side has a wired receiving packet receiving part 20 which determines whether or not an address of a wired packet received from the wired network corresponds to an address by radio, a real time determination part 21 which determines whether or not a wired packet determined as the address to be sent by radio is a real time packet requiring real time property and a fragment processing part 24 which generates a division packet by dividing the wired packet determined not to be the real time packet by a prescribed data length.