A glass fiber according to the present invention is suitable for preventing filament breakage and suitable for being stably produced for a long term, and has a β-OH value of 0.02 mm -1 or more and less than 0.55 mm -1 . The preferred content of SO 3 is more than 0 ppm and 70 ppm or less on a mass basis. The glass fiber is preferably substantially free of As and Sb. SO 3 can be supplied to a glass raw material as, for example, a sulfuric acid salt of an alkali metal or an alkaline-earth metal.