A packet-relay unit 100 including a first interface unit (110), a second interface unit (120), and a function-setting switch (130). The second interface unit (120) includes a classifying unit (121), a priority control unit (122), and a transceiving unit (123). When the function-setting switch (130) sets a “QoS function” as “operative”, the classifying unit (121) transfers packets transferred from the first interface unit (110) to the priority control unit (122). The priority control unit (122) provides priority control over the transferred packets such that the transferred packets are preferentially treated at a wireless zone connected to the second interface unit (120), whereby the priority-controlled packets are transferred to a transceiving unit (123) from the priority control unit (122). When the function-setting switch (130) sets “the QoS function” as “inoperative”, the classifying unit (121) transfers the transferred packets directly to the transceiving unit (123).