Abstract: In order to contribute to the improvement in the efficiency of an exhaustive verification of a network, a network verification device is provided with: a verification information input unit which accepts an input of verification information that defines the configuration of a network to be verified and the operation model of a device included in the network; a model checking execution unit which, in model checking using the verification information, performs a state transition without concretely dealing with the contents of a packet from a terminal connected to the network, sends information relating to the past transition path of each state to a search necessity/unnecessity confirmation unit before a state search of a next state, and performs the model checking while inquiring whether or not the search of the next state can be omitted or not; the search necessity/unnecessity confirmation unit which, based on the information relating to the past transition path of the state and received from the model checkin