PURPOSE: To obtain the flexible optical fiber bundle which transmits sharp images by bundling optical fibers of acid elution glass containing a light absorber around the peripheral part of a center optical fiber, and causing the acid elution of the acid elution glass so that the light absorber remains.

CONSTITUTION: Core glass 1 with a relatively high refractive index is coated with acid proof coating glass 2 with a relatively low refractive index. Further, the acid elution glass 3 containing the light absorber covers its outside. Numbers of fibers 4 are bundled and further surrounded with optical fibers 5 which contain the light absorber. This optical fiber bundle in a glass jacket 6 is heated and drawn, and then cut into conduits 11. Then, both ends of a conduit 1 are finished by polishing, sealed with a heat-shrinkable tube 12, and dipped in nitric acid 14. Consequently, acid elution glass is eluted in nitric acid and the light absorber remains. Consequently, the flexible optical fiber which provides sharp transmitted images is obtained.