Glass fiber production method

Provided is a method for producing glass fiber, capable of stably performing the spinning of glass fibers without mixing of red crystals in glass fibers. When glass fibers are formed by discharging, from a nozzle tip, a molten glass obtained by melting glass raw materials mixed so as to give a glass composition including, when melted, in relation to the total amount thereof, SiO2 in a range from 57.0 to 62.0% by mass, Al2O3 in a range from 15.0 to 20.0% by mass, MgO in a range from 7.5 to 12.0% by mass, and CaO in a range from 9.0 to 16.5% by mass, and having a total content of SiO2, Al2O3, MgO and CaO of 98.0% by mass or more, the glass composition includes B2O3, Li2O, or B2O3 and Li2O as an additive or additives capable of suppressing the generation of red crystals.