PURPOSE:To remove a jacket with a slight force and to expose an optical fiber core by cutting >=2 longitudinal cutting lines and drawing the jacket in mutual spreading directions, and tearing the jacket along the cutting lines. CONSTITUTION:The >=2 longitudinal cutting lines 3 are made and the jacket 2 is drawn in the spreading directions, and torn along the cutting lines 3. Namely, the jacket 2 is drawn in the spreading directions to expose the center part including the fiber core 5 to the outside in a natural state wherein it is not bent at all. In this drawing and tearing, the part except the jacket 2 need not be applied with a force and the tensile force in the spreading directions operates directly on the parts of the jacket 2 along the cutting lines 3. Consequently, the jacket is torn with the slight force and no lateral force is applied to the fiber core 5.