A network simulation device of the present invention: accepts an input of first plane information being positional information on a network projected onto a coordinate plane having any two dimensions out of three dimensions as coordinate axes; creates network model information which defines a coordinate value of the remaining one dimension as unknown based on the accepted first plane information; accepts selection of the element having the coordinate value defined as unknown by a user from the elements which appear in the first plane information; accepts an input of second plane information being positional information on the network projected onto a coordinate plane having any two dimensions including the remaining one dimension as coordinate axes; and determines a numerical value of the coordinate value defined as unknown of the selected element in the created network model information based on the accepted second plane information.