An upstream allocation circuit (14) and a downstream allocation circuit (15) are provided in an OLT (1). For example, a superimposed frame obtained by bundling upstream frames (upstream control frames+upstream data frames) from all ONUS is input to the upstream allocation circuit (14) via a frame reproduction circuit (12-1). The superimposed frame may be generated at the stage of optical signals or generated after converting optical signals into electrical signals. The upstream allocation circuit (14) allocates each of the upstream control frames bundled into the superimposed frame to a predetermined PON control circuit (13) based on information (PON port number or LLID) added to the frames. The downstream allocation circuit (15) allocates, to a preset frame reproduction circuit (12), each downstream control frames output from the PON control circuits (13).