Abstract: An optical transmission/reception module in which an LD, a lens holder, which supports a lens, a partial wave filter, a lens holder, which supports a lens, and an optical fiber are all mounted to a housing block, coaxially along a first axis. A reflecting mirror, a lens holder, which supports a lens, and a PD are also mounted to the housing block, coaxially along a second axis which is parallel to the first axis. Cutouts are formed in the housing block for providing large openings forwardly of and perpendicular to a mounting surface for mounting the partial wave filter thereon and a mounting surface for mounting the reflecting mirror thereon. In such an optical transmission/reception module, it is possible to maintain the precision with which a partial wave filter, which passes a transmission light therethrough, and a reflecting member, which reflects a reception light, are mounted to a desired mounting angle at a high level, and to reduce assembly costs.