In an open flow system, it is made possible to confirm a flow having succeeded or failed in the registration on a flow table. Specifically, a controller transmits and receives an open flow message to and from a switch. The switch is provided with a flow table which manages flows registered from a controller, and a flow table reading section which reads corresponding data, a flow table control section which performs processing of addition, deletion and modification of a flow entry, and a platform function managing section which determine whether an object flow entry is valid or invalid according to an inquiry from the flow table control section. The flow table has a normal flow table and a save flow table. A valid flow entry which conforms to configuration data of the switch is registered on the normal flow table. An invalid flow entry which does not conform to the configuration data of the switch is registered on the save flow table.