The composition comprises a compound (A) represented by general formula (1) and a compound (B) represented by general formula (2), and comprises 0.00002 to 2.0 parts by mass of the compound (B) with respect to 100 parts by mass of the compound (A),

(R1—COO)n—R2—(NCO)m  (1)

(R1—COO)n—R2—NHC(═O)NH—R2—(OCO—R1)m  (2)

wherein in general formulae (1) and (2), R1 is an ethylenically unsaturated group having 2 to 7 carbon atoms; R2 is a (m+n)-valent hydrocarbon group having 1 to 7 carbon atoms and optionally contain an ether group; R1 and R2 in the general formula (1) are the same as R1 and R2 in the general formula (2); and n and m each represent an integer of one or two.