A logical-link management method to be executed in an optical communication system including a station side device (OLT) and a subscriber side device (ONU) that is capable of setting a plurality of logical links together with the OLT, in which the OLT transmits a signal for managing the ONU via a single logical link. The logical-link management method includes a status monitoring of the OLT monitoring whether there is a change in a connection status of the logical link between the OLT and the ONU and a link resetting of the OLT resetting, when a change of the connection status of the logical link is detected at the status monitoring, a device management logical link used for transmitting the signal for managing the ONU according to a predetermined procedure.