A packet relay device which realizes a QoS service with higher quality by improving an intra-device policy concerning packet discard. An input-side policing unit measures a first data rate of packets before being switched, and discards at least one of the packets before being switched, when the first data rate exceeds a first bandwidth value which is preset. A switching unit performs switching of the packets on which the input processing is performed. An output-side policing unit receives packets flowing together after being switched, measures a second data rate of a portion of the received packets corresponding to each value of a parameter, compares the second data rate with a second bandwidth value which is preset to be guaranteed for the value of the parameter, and discards at least one packet in the portion of the received packets when the second data rate exceeds the second bandwidth value.