A network switching device includes: a communication unit; an information collection unit configured to obtain information on a network state of the network from first and second information for packets received through the communication unit; a marking reference calculation unit configured to calculate a marking reference based on the second information when it is determined that the network state has changed based on the first information; and a marking execution unit configured to perform marking indicating a congestion degree on at least a part of the packets received through the communication unit based on the calculated marking reference.