a glass fiber including a core and a cladding; and

a coating resin layer coating the glass fiber in contact with the glass fiber,

wherein the coating resin layer has a primary resin layer coating the glass fiber in contact with the glass fiber and a secondary resin layer coating the primary resin layer,

the primary resin layer comprises a cured product of a first resin composition containing a photopolymerizable compound and a phosphine oxide-based photopolymerization initiator,

the secondary resin layer comprises a cured product of a second resin composition containing a photopolymerizable compound and a phosphine oxide-based photopolymerization initiator,

an amount of the phosphine oxide-based photopolymerization initiator remaining unreacted in the coating resin layer is 0.5 mass % or less, and

the first resin composition and the second resin composition do not contain any photopolymerization initiators other than the phosphine oxide-based photopolymerization initiator.