Provided is an optical fiber which is provided with heat resistance and productivity and in which a transmission loss is suppressed even in a high-temperature environment. It has, on an outer periphery of a glass fiber composed of a core part and a cladding part, a coating layer made by crosslinking an energy-curable resin composition containing a silicon compound, in which the silicon compound contained in the energy-curable resin composition of the coating layer as an outermost layer has a specified structure having a cyclic silicone site having an epoxy group and a linear silicone site, with the content of the cyclic silicone site in the compound being from 10 to 30% by mass.