An optical fiber manufacturing method includes supplying power to a drawing furnace to cause T/V to decrease to T.sub.target/V.sub.target along a quadratic function having a value of the T.sub.target/V.sub.target at an apex with lapse of time, where T is a tension applied to an optical fiber when an optical fiber preform is heated by the drawing furnace and the optical fiber is drawn, V is speed of withdrawing the optical fiber when the optical fiber is heated by the drawing furnace and the optical fiber is drawn, T.sub.target is a target value of the tension, and V.sub.target is a target value of the speed.

Provided is an optical fiber glass preform, in a preliminary step of a final drawing step, in which the optical fiber glass preform is undergone one or more drawing steps to be drawn to a final target diameter, wherein as an outer diameter of an effective portion of the glass preform is continuously measured in a longitudinal direction, and from outer diameter measurement results obtained, a regression line of y=ax+b is obtained using the least squares method with y as the outer diameter and x as a length, an absolute value of a slope a is less than or equal to 0.005 mm/mm; and a maximum value of an obtained absolute value of a curvature of the outer diameter at any given point, in the outer diameter measurement results obtained, is 0.003 or less.