An optical fiber coupling part capable of reducing coupling loss while maintaining a large operating distance, and having a good module assembling property. AT least one GRIN lens having numerical aperture NA that is larger than numerical aperture NAs of a light-emitting source (such as a semiconductor laser) is fusion-spliced with one end of the optical fiber. All lights emitted from the light-emitting source can enter the GRIN lens, and the loss of the light can thereby be reduced. In addition, a second GRIN lens having numerical aperture NA2 is fusion-spliced with one end of the optical fiber having numerical aperture NAf, and further a first GRIN lens having numerical aperture NA1, which is larger than numerical aperture NA2, is fusion-spliced with the other end of the second GRIN lens. Thereby, the light emitted from the light-emitting source can efficiently enter the optical fiber, and loss of the light can thereby be reduced. In this case, the formula expressed by NAf≦NA2<NAs≦NA1 is desirable.