The invention provides a method of forming a high-performance thin-film at low cost using a liquid material in safety, an apparatus to form a thin-film, a method of manufacturing a semiconductor device, an electro-optical unit, and an electronic apparatus.An apparatus to form a thin-film includes a coating unit to apply a liquid material containing a thin-film component onto a substrate and also includes heat-treating units to heat the substrate applied with the liquid material. The coating unit and the heat-treating units each include a control device to control the atmosphere in a treating chamber to treat the substrate.