Provided is an apparatus for guaranteeing the performance of Ethernet packets in an Ethernet system. A packet sorting unit receives the Ethernet packets, processes header information of the Ethernet packets, and sorts the Ethernet packets. A packet processing unit stores the Ethernet packets, calculates the number of the Ethernet packets, and outputs the Ethernet packets. A packet to synchronous digital hierarchy frame converting unit receives the Ethernet packets output from the packet processing unit, converts the received Ethernet packets into synchronous digital hierarchy frames, calculates the number of the converted frames, maps the frames to a virtual container group, and outputs the virtual container group. And a signal processing unit measures the performance of the Ethernet packets on the basis of the number of the Ethernet packets stored in the packet processing unit and the number of the frames, and outputs the first and second control signals.