Abstract: Provided are a relay apparatus and a relay method for a passive optical network so as to largely extend a communicable distance while maintaining compatibility with existing network components. In the case of applying an optical relay to the passive optical network, a delay time is reduced by applying the optical relay so that entire transmission delay time considering the increased delay time may be within a preamble period of the upstream burst stream, thereby rapidly increasing a transmission distance of the passive optical network by using the optical relay.