To solve the problem wherein there is a risk that appropriate control of QoS cannot be made, depending on the causes which generate communication errors, in a wire or radio network.

An error-pattern analysis section 109 specifies the position of an abandoning packet in a continuously transmitting packet group (a group) (S808). The QoS control section 110 controls the QoS, corresponding to the causes generating the communication errors, on the basis of the position specified by the error-pattern analysis section 109 (S810-S822).