An optical fiber was embedded between two central laminates of the specimen, and the influence of the embedded optical fiber on interlaminar shear strength was investigated. First, the interlaminar shear strength (ILSS) was measured by a short beam three point bending method. The Optical fiber was embedded parallel to the reinforced direction (specimen type A), or perpendicular to the reinforced direction (specimen type B). The result of interlaminar shear test showed that in the specimens of type A, there was no noticeable deterioration on ILSS. In the specimens of type B, as the distance between the loading point and the optical fiber increases, ILSS decreased slightly, and the position of fracture surface shifted toward the embedded optical fiber. Secondly, the distribution of the volume fraction of reinforced fibers along the thickness direction was measured by thresholding technique of image processing. In the specimen in which the optical fiber was embedded perpendicular to the reinforced direction, the volume fraction of fibers increased significantly near the embedded optical fiber. It was considered that this increase in volume fraction of fibers influenced the deterioration of ILSS. Thirdly, to discuss the shift of fracture surface, the stress distribution was analyzed by using finite element analysis. At the position of the specimen where the optical fiber was embedded, two shear stress peaks can be seen inside of the composite. This result shows that the embedded optical fiber changes the stress distribution around the optical fiber and causes the shift of fracture surface.