1. A network model integration device comprising: an input unit; a display unit; a storage unit; and a control unit, wherein the storage unit includes: a network model storage unit that stores a network model that includes nodes that represent constituent elements of a biological object and edges that represent interactions between the constituent elements and a network model ID that identifies the network model in association, and the control unit includes: a retrieving unit that, when the network model is designated by a user via the input unit, retrieves the edges that are stored in the network model storage unit, do not constitute a designated network model which is the network model, and are linked to the nodes that constitute the designated network model, a retrieval result displaying unit that displays retrieval results including the edges retrieved by the retrieving unit and the network model ID that identifies the network model including the edges stored in the network model storage unit on the display unit in a selectable manner, an integrating unit that, when the retrieval results displayed on the display unit by the retrieval result displaying unit are selected by the user via the input unit, generates an integrated network model which is the network model in which the edges included in the selected retrieval results and the nodes that do not constitute the designated network model and are linked to the edges are integrated into the designated network model, a network model storing unit that acquires the network model ID that identifies the integrated network model generated by the integrating unit and stores the integrated network model and the network model ID in the network model storage unit in association, and a keyword acquiring unit that, when a portion or all of the network models, the nodes, or the edges are selected by the user via the input unit, acquires keywords related to the portion or all of the network models, the nodes, or the edges.