Provided are a method and apparatus for manufacturing fiber gratings capable of removing or reducing birefringence and polarization-dependence caused by fiber gratings, and an optical fiber having the fiber gratings formed thereby. The method includes: selectively exposing an optical fiber to a light source, and generating first fiber gratings on the optical fiber; and selectively exposing the optical fiber to a light source on a region spaced apart from the first fiber gratings in a longitudinal direction at a different angle from the first fiber gratings about an axis of the optical fiber, and generating second fiber gratings that are the same as the first fiber gratings. Use of the method and apparatus for manufacturing fiber gratings may effectively remove or reduce birefringence or polarization effects.