An optical fiber comprising: a core extending along a fiber axis and comprised of silica glass; a cladding provided on an outer peripheral surface of the core, comprised of silica glass, and having a maximum refractive index lower than a maximum refractive index of the core; and a resin coating (63, 64) provided on an outer peripheral surface of the cladding, wherein the optical fiber has a mode field diameter of 8.2 μm or more and 9.6 μm or less at a wavelength of 1310 nm, a cable cutoff wavelength of an LP11 mode of 1060 nm or more and 1260 nm or less, and a cable cutoff wavelength of an LP02 mode of 1060 nm or less, a radius of the core defined along a radial direction orthogonal to the fiber axis is 3 μm or more and 10 μm or less, the core includes an inner region surrounded by an outer peripheral surface that is around the fiber axis as a center and is separated from the fiber axis by 0.2 times the radius of the core, and in the inner region, a refractive index profile of the core has a shape in which a relative refractive index at a core center coinciding with the fiber axis is 0.8 times or more a maximum refractive index difference of the core, characterized in that in an outer region of the core surrounding the inner region, the refractive index profile of the core has a shape in which a relative refractive index difference Δ0 defined in the inner region in which a distance r0 along the radial direction satisfies a relationship of 0 ≤ r0/r1 ≤ 0.2 with respect to a distance r1 corresponding to the radius of the core, the relative refractive index difference Δ0 being a refractive index difference at a portion separated from the fiber axis by the distance r0, a relative refractive index difference Δ1 at a portion separated from the fiber axis by the distance r1, and a relative refractive index difference Δ r at a portion separated from the fiber axis by a distance r equal to or greater than the distance r0 and equal to or less than the distance r1 satisfy a relationship approximated by the following formula including an exponent α of 2.0 or more and 20 or less: Δ r = Δ 0 + Δ 1 − Δ 0 × r − r 0 / r 1 − r 0 α a core extending along a fiber axis and comprised of silica glass; a cladding provided on an outer peripheral surface of the core, comprised of silica glass, and having a maximum refractive index lower than a maximum refractive index of the core; and a resin coating (63, 64) provided on an outer peripheral surface of the cladding, wherein the optical fiber has a mode field diameter of 8.2 μm or more and 9.6 μm or less at a wavelength of 1310 nm, a cable cutoff wavelength of an LP11 mode of 1060 nm or more and 1260 nm or less, and a cable cutoff wavelength of an LP02 mode of 1060 nm or less, a radius of the core defined along a radial direction orthogonal to the fiber axis is 3 μm or more and 10 μm or less, the core includes an inner region surrounded by an outer peripheral surface that is around the fiber axis as a center and is separated from the fiber axis by 0.2 times the radius of the core, and in the inner region, a refractive index profile of the core has a shape in which a relative refractive index at a core center coinciding with the fiber axis is 0.8 times or more a maximum refractive index difference of the core, characterized in that in an outer region of the core surrounding the inner region, the refractive index profile of the core has a shape in which a relative refractive index difference Δ0 defined in the inner region in which a distance r0 along the radial direction satisfies a relationship of 0 ≤ r0/r1 ≤ 0.2 with respect to a distance r1 corresponding to the radius of the core, the relative refractive index difference Δ0 being a refractive index difference at a portion separated from the fiber axis by the distance r0, a relative refractive index difference Δ1 at a portion separated from the fiber axis by the distance r1, and a relative refractive index difference Δ r at a portion separated from the fiber axis by a distance r equal to or greater than the distance r0 and equal to or less than the distance r1 satisfy a relationship approximated by the following formula including an exponent α of 2.0 or more and 20 or less: Δ r = Δ 0 + Δ 1 − Δ 0 × r − r 0 / r 1 − r 0 α