A transmitting and receiving circuit includes an optical circuit for transmitting and receiving data from and to a facing node, and a speed negotiation state machine for executing a speed negotiation to find a maximum value of a data transfer speed in a channel between nodes before data transfer to the facing node, and setting the thus obtained maximum value as a maximum transfer speed of each transceiver. With this, the speed negotiation is executed with the facing node for each transceiver before data transfer, and the transfer speed of the node is determined by the result of the speed negotiation, so that it is possible to provide a transmitting and receiving circuit and a transmitting and receiving method such that data transfer becomes possible even in a channel of poor quality.