An optical-fiber feedthrough formed of a metallic sleeve 1 and an optical fiber 2 fastened thereto. The the metallic sleeve 1 has i) a sleeve main body having a first hollow portion 9 which has an inner diameter larger than the outer diameter of the optical-fiber bare fiber uncovered portion 3 in the optical fiber 2 and into which the optical-fiber bare fiber uncovered portion is inserted, and a second hollow portion 8 which communicates with the first hollow portion and has an inner diameter larger than the outer diameter of the resin-covered portion 5 in the optical fiber and in which an inserted portion of the resin-covered portion and an optical-fiber bare fiber uncovered portion standing uncovered from the resin-covered portion to lead to the first hollow portion are held and ii) a first conical recessed portion 10 which is provided on the first hollow portion side of the sleeve main body and to which the leading end portion of the optical-fiber bare fiber uncovered portion is uncovered.