Abstract: Provided are a node device and a method for deciding a shortest path using a spanning tree. The node device includes: a node division unit dividing the node device into sub-nodes as many as the number of nodes connected to the node device when the node device operates an edge node that is located at an end of a backbone network and is in charge of reformatting and routing frames; a spanning tree generation unit generating as many spanning trees as the number of sub-nodes, wherein each of the spanning trees comprises a shortest path to reach the other edge nodes constructing the backbone network from each of the sub-nodes; and a first path decision unit deciding a shortest path from a source node to a predetermined destination node, as a path to be used, based on the spanning trees that are generated by the spanning tree generation unit. The shortest path that is obtained based on the plurality of spanning trees is used as a path to be used such that throughput of traffic is 3 times and 1.