An optical transmission apparatus includes redundant line cards each having a plurality of ports, a hardware unit and a CPU. The hardware unit obtains failure information on redundant lines for each port. The CPU determines switching control of the redundant lines based on the failure information. Then, the hardware unit switches the redundant lines based on the switching control determined by the CPU, so as to transmit an SDH/SONET optical signal in a ring network. The CPU of one of the line cards is set as a master CPU on the corresponding line card to control switching of the redundant lines. Further, the CPU of the other line card is set as a slave CPU.