A network device of is a network device that transfers frames by repeating, in a constant cycle, a reserved transfer interval and a free transfer interval. The network device includes a transmission port, a cycle timer, a mode switching control unit that monitors a transfer state of the transmission port and selects a store-and-forward system when the transmission port is in the transfer process and selects a cut-through system when the transmission port is not in the transfer process, and a transfer prohibition control unit that selects the cut-through system as a transfer system when a non-reserved frame is transmitted and switches a transfer method of the non-reserved frame to the store-and-forward system when a reserved transfer interval is established, with reference to the cycle timer.