The input output control device is provided with a plurality of fiber channel interface circuits and a protocol processing circuit capable of sequentially executing the protocol processing of each port, and is provided with a reception port identification register capable of identifying the port handling data to be received and a transmission port designation register designating the port handling data to be transmitted. In addition, it is possible to provide a controller using jointly the data buffers concerned with the plurality of ports. Control of a plurality of fiber channel interfaces with a low component count is possible, as is also the provision of an input output control device making an adequate capacity distribution with respect to the protocol processing between the plural fiber channel interfaces.