According to the present invention, there is provided a covering composition for optical fiber comprising (A) an unsaturated polyester oligomer having substantially two or more (meth)acryloyl group in a molecule wherein a glass transition temperature of a cured substance thereof is 100 to 350 C.; (B) at least one oligomer selected from the group consisting of the following components: (B-a) epoxy modified (meth)acrylate oligomer, (B-b) polyether polyol modified (meth)acrylate oligomer, and (B-c) urethane polyether polyol modified (meth)acrylate or urethane polyester polyol modified (meth)acrylate; and (C) a photopolymerization initiator, as essential components. The cured material has highly elasticity and is superior in the heat stability, and as a result, the present invention provides the superior covered optical fiber with well balanced heat stability of the optical transmission properties and flexibility.