To provide an optical fiber having high compatibility with respect to G.652 standard and a further smaller diameter, the optical fiber includes a core portion made of silica based glass; a cladding portion made of silica based glass and configured to cover an outer periphery of the core portion, the cladding portion having a refractive index that is lower than a maximum refractive index of the core portion; and a coating portion configured to cover an outer periphery of the cladding portion, the coating portion including a primary coating layer located on the cladding portion side and a secondary coating layer located on an outer peripheral side of the primary coating layer. An outer diameter of the cladding portion is less than 100 µm, a thickness of the primary coating layer is larger than or equal to 15 µm, a mode field diameter at a wavelength of 1310 nm is larger than or equal to 8.6 µm and smaller than or equal to 9.2 µm, an effective cutoff wavelength is smaller than or equal to 1260 µm, and a bending loss at a wavelength of 1550 nm when bending is made at a diameter of 60 mm is smaller than or equal to 0.1 dB/100 turn.