Disclosed is a bidirectional optical add/drop multiplexer that includes a first filter for reflecting a first optical signal pre-selected among input forward optical signals and transmitting the remaining forward optical signals, a second filter for reflecting a second optical signal pre-selected among input reverse optical signals and transmitting the remaining reverse optical signals, a first optical splitter for combining the first optical signal and the forward optical signals by reflection from the first filter, wherein the reflected second optical signal having passed through the first filter is outputted to a connected second drop terminal and the first optical signal input from a connected first add terminal is outputted to the first filter, and a second optical splitter for adding the second optical signal and the reverse optical signals by reflection from the second filter, wherein the reflected first optical signal having passed through the second filter is outputted to a connected first drop terminal and the second optical signal input from a connected second add terminal is outputted to the second filter.