A plastic optical fiber and a method for producing the same is disclosed. The plastic optical fiber is formed as a fiber of core-cladding structure. A protective layer or shield layer may be provided on the outer surface of the optical fiber of core-cladding structure for improving thermal resistance of the optical fiber and protecting the optical fiber from air and moisture. The plastic optical fiber uses fluorinated plastic, which contains a rare earth component as a core material, and a cladding material, which does not comprise a rare earth component but essentially consists of a polymer chain, which essentially consists of bonded —[CF₂]_n— monomers and has a refractive index lower than that of the core material. The optical fiber is produced by a melting-drawing technique.