Provided is a topology discovery method for an Ethernet network that can effectively discover a physical topology with respect to the Ethernet network of a mesh structure without developing and using a separate control protocol. The topology discovery method in an Ethernet network includes the steps of: acquiring an interface management information base (MIB) and a bridge MIB; defining and storing information for discovering a physical topology; discovering an edge bridge that divides a boundary between a bridge network and a host network; discovering the physical topology with respect to the bridge network by using the schema; discovering the connection relationship with the host network by using an address learning address forwarding table (AFT) with respect to the edge bridge included in the bridge network; and outputting the connection relationship of the bridge network and the host network as a graph.