PURPOSE: The titled composition, containing a specific urethane acrylate, specific monofunctional acrylate and specific polyfunctional acrylate in a specific proportion, having a low glass transition point, low elastic modulus and improved heat aging resistance, etc., and suitable as an optical fiber coating material.

CONSTITUTION: A composition containing (A) 20W80wt% urethane acrylate, etc., obtained by reacting a diisocyanate with both terminals of polytetramethylene glycol having 1,500W10,000 molecular weight and further reacting the resultant product with a compound having (meth)acryloyl group and OH group and having (meth)acryloyl groups at both terminals, (B) 20W80wt% monofunctional acrylate expressed by the formula (R1 is H or CH3) and (C) 2W35wt% polyfunctional acrylate having ≥2 acrylate groups in one molecule.