To obtain a glass fiber capable of obtaining an FRTP excellent in mechanical strength and resistant to hot water even if a urethane resin is used as a film forming agent and keeping a good sizing property even when the amt. of a binder to be deposited is decreased by using the glass fiber coated with a binder contg. sodium borohydride.

The amt. of sodium borohydride to be deposited is preferably controlled to 0.01-5 wt.%. A urethane resin or the urethane resin and an epoxy resin are used as the film forming agent of the binder, and a coupling agent based on silane, titanate, etc., a lubricant, an antistatic agent, etc., are added, as required. A remarkable effect is obtained when polyphenylene sulfide is used as the matrix resin of the FRTP. The ratio of the glass fiber to matrix resin is appropriately adjusted to 2-80 wt.%.