A process for forming a pattern which comprises irradiating with light a film of a poly(arylenevinylene) polymer represented by the following formula (I) --(Ar--CR.sup.1 =CR.sup.2).sub.n -- (I) wherein Ar is a substituted or unsubstituted divalent aromatic hydrocarbon group or a substituted or unsubstituted divalent heterocyclic ring group, and the aromatic hydrocarbon group and the heterocyclic ring group may be a fused ring, R.sup.1, R.sup.2 independently of each other, are H, CN, alkyl, alkoxy are substituted or unsubstituted aromatic hydrocarbon groups or substituted or unsubstituted aromatic heterocycles, which may both be fused rings, and n is an integer of 2 or more. It is preferred that either R.sup.1 or R.sup.2 is H and more preferred that both R.sup.1 and R.sup.2 are H.