A system according to this invention is directed to a virtual network system that prevents unauthorized registration, alteration, or occurrence of erroneous registration when registering a virtual network function produced by a third party or system vender. The virtual network system includes an acceptor that accepts a virtual network function performing one of functions included in a virtual network service and information of a provider providing the virtual network function from the provider, a first authenticator that authenticates, based on the virtual network function and the provider information, that the provider is a valid provider, and a registration unit that registers the virtual network function when the first authenticator authenticates that the provider is a valid provider.