A packet processing apparatus includes a packet buffer with a queue for storing packets. An actual queue length/position discriminator acquires, at every sampling period, the latest actual queue length indicating the occupancy status of the queue, determines the positional relationship of the actual queue length to a random early detection interval, and outputs the positional relationship as position information. A discard probability computation processor calculates, at every sampling period, a packet discard probability based on the position information. A packet discard processor discards, at every sampling period and in accordance with the discard probability, packets that are not yet stored in the queue. If it is judged from the position information that the actual queue length is within the random early detection interval, the discard probability computation processor calculates an average queue length, and then calculates the discard probability from the ratio of a discard target to a reception target.