A transmission/reception optical module has an optical transmission subassembly 182, an optical reception subassembly 183, and a circuit board 1 wherein the circuit board 1 is formed into one member by a rigid/flexible substrate. Circuit board main bodies 2a, 2b, and an optical reception subassembly fixation region 4 are formed by rigid regions 5A, 5b, and 5P. An area provided between the circuit board main body 2a and the optical reception subassembly 4 is composed of a flexible region 6P. A part of the circuit board main body 2 is composed of a flexible region 6.