A film forming composition includes a polymer of a compound represented by formula (I): ##STR00001## wherein R.sup.1, R.sup.2 and R.sup.3 each independently represents a substituent containing a carbon-carbon double bond or carbon-carbon triple bond; X.sup.1, X.sup.2 and X.sup.3 each independently represents any substituent; l and n each stands for an integer of from 0 to 15 and m stands for an integer of from 0 to 14, with the proviso that l, m and n do not represent 0 simultaneously; o and q each independently stands for an integer of from 0 to 15 and p independently stands for an integer of from 0 to 14; and r stands for 0 or 1, with the proviso that when r=0, R.sup.1 and R.sup.3 each independently represents a substituent containing a carbon-carbon double bond.