The thin film-forming material of the present invention comprises a bis(.beta.-diketonato)zinc compound that is liquid at 25.degree. C. and is suitable for forming a zinc-containing thin film. By using the thin film-forming material, a thin film can be produced with stable film-forming rate or stable film composition control without suffering from problems of raw material gas suppliability and in-line raw material transport. Preferred (.beta.-diketonato)zinc compounds are bis(octane-2,4-dionato)zinc and bis(2,2dimethyl-6-ethyldecane-3,5-dionato) zinc.