To provide an optical fiber whose color is easily identified, even in a dim environment where no sufficient illuminance can be obtained, and with which workability can be improved.

The coating layer 2 of an optical fiber is formed with a coating material in which a luminescent material is mixed. Also, if the coating layer 2 of an optical fiber is multilayered, the outermost coating layer 2b is formed with a colored coating material in which a luminescent material is mixed. Further, if a color painted layer is installed on the whole or part of the outer circumferential face of the coating layer of the optical fiber, the color painted layer is formed with the one mixed with a luminescent material.