An optical fiber comprises a glass fiber including a core and a cladding surrounding the core, a non-strippable resin layer that adheres to and covers a surface of the glass fiber, and a buffer layer that covers the non-strippable resin layer, when pullout force measurement in which a length of 10 mm of each of the glass fiber and the non-strippable resin layer is pulled out at a tensile speed of 5 mm/min from the buffer layer is performed, a pullout force at 23° C. is 1.0 kg or less and a pullout force at 95° C. is 0.50 kg or less.