An optical fiber capable of achieving both of the ZSA property and the rapid curability is provided. The optical fiber includes a glass optical fiber 13, a primary coating layer 16 that coats an outer periphery of the glass optical fiber 13, and a secondary optical fiber 17 that coats an outer periphery of the primary coating layer 16. Young's modulus of the primary coating layer 16 is 1.2 MPa or less and Young's modulus of the secondary coating layer 17 is 800 MPa or more. Sulfur content of the surface of the glass optical fiber 13 is 0.2% by atom or more. Sulfur is not present in the vicinity of the outer periphery of the primary coating layer 16.