A graded-index multimode fiber includes a core containing fluorine and a cladding which is provided at an outer periphery of the core, and the fiber has a refractive index profile which satisfies the following Formula (1):

##EQU1##

• where n(r) is a refractive index of the optical fiber at a distance "r" from the center of the core, n₁ is a refractive index at the center of the core, is a relative refractive index difference of the center of the core with respect to the cladding, "a" is a core radius, and is a refractive index profile exponential parameter.