A clamp to be surface mounted on a printed circuit board with a clamp groove into which an optical fiber is inserted. A flexible synthetic resin member is deformed by applying a pressing force so as to narrow the width of the clamp groove. The deformation causes an opening of the clamp to be closed, and opposing shape preservation members with the clamp groove located therebetween to be deformed so as to shorten the distance between top ends of the shape preservation members. A metal plate member with no spring properties remains deformed even after the pressing force is released, and the flexible synthetic resin member also remains deformed. An optical fiber pinched by inner wall surfaces of the clamp groove is unlikely to be displaced either in an axial direction or in a radial direction.