An optical fiber propagates a light beam at a predetermined wavelength at least in an LP01 mode and an LP02 mode. A dopant that changes a Young's modulus is doped to at least a part of a waveguide region 12a of a cladding 12 through which a light beam at a predetermined wavelength is propagated and to a region 11b in a core 11 in which the intensity of the light beam in the LP01 mode is greater than the intensity of the light beam in the LP02 mode. At least a part of the Young's modulus in the waveguide region 12a of the cladding 12 is smaller than a Young's modulus in the region 11b in the core 11 in which the intensity of the light beam in the LP01 mode is greater than the intensity of the light beam in the LP02 mode.