An optical fiber includes a core having a maximum refractive index n1, and cladding provided around the core and having a refractive index n0 that is lower than the maximum refractive index n1. A radial refractive-index profile of the core is expressed with an exponent α that is 1.5 to 10. A relative refractive-index difference Δ1 at a center of the core that is expressed as Δ1=100×(n12−n02)/(2n12) is 0.3% to 0.5%. A diameter 2a of the core is 9 μm to 14 μm. A zero-dispersion wavelength is 1300 nm to 1324 nm. A cable cutoff wavelength λcc is 1260 nm or shorter. A bending loss at a wavelength of 1550 nm in a case where the optical fiber is wound by ten turns with a bend diameter of 30 mm is 0.25 dB or smaller.