A switching circuit connected to an I/O device having a plurality of functions, the switching circuit comprising: a processing unit that includes tables, each of which corresponds to one of the function of the I/O device, when the processing unit receives a packet that instructs to add a function to the I/O device, configured to select the table that contains a bus number of a destination of the received packet, and configured to notify a number of the selected table; and a filter configured to change a function number of the destination of the received packet to the number of the table notified from the processing unit.