An input switching device is provided between a plurality of functional blocks (NoC routers or IP) connected to a specific router among a plurality of NoC routers of a NoC system and the specific router. The specific router includes a plurality of first buffers that temporarily store flits from the input switching device. A plurality of second buffers in the input switching device correspond to the respective one of the plurality of functional blocks, and temporarily store the flits from the functional block. A controller selectively sets one of the plurality of first buffers as output destination of the flit stored in each of the second buffers based on a free space of the plurality of first buffers. A distributor outputs the flit stored in each of the second buffers to output destination set for the flit by the controller.