Multi-core fibers are optical fibers each of which has a circular cross section. In each of the multi-core fibers, a plurality of cores are arranged at a prescribed interval, the peripheries thereof are covered by a cladding, and a resin coating is formed on the outer periphery of the cladding. In a cross section of this optical fiber ribbon, said cross section being orthogonal to the length direction, the multi-core fibers are arranged such that the cores of all of the multi-core fibers are all arranged in the same direction. The multi-core fibers are arranged such that central lines of the respective multi-core fibers, said central lines respectively linking three of the cores, all face the thickness direction of the optical fiber ribbon. Furthermore, in the optical fiber ribbon, the arrangement of the cores is substantially constant along the entire length of the optical fiber ribbon in the length direction.