An Ethernet® communication system wherein control signals are relayed by ADM/WDM apparatuses and are directly transferred between L2/L3 switches apparatuses to enable application for new control protocols, improvement of the maintenance ability, etc., that is, an Ethernet® communication system provided with at least two transmission apparatuses arranged opposing each other across a transmission line at which an Ethernet® path is set and terminating units connected to the transmission apparatuses and communicating between terminating units through said transmission apparatuses, wherein each of the transmission apparatuses is provided with a relaying means for relaying communications by insertion of control signals transferred by interfaces of the terminating units, without termination at the transmission apparatus, into Ethernet® frames between the transmission apparatuses, and the control signals are passed through the relaying means to the opposing side terminating unit.