A method of forming a semiconductor thin film includes the steps of: forming an amorphous semiconductor thin film on a substrate; forming a crystalline semiconductor thin film partially in each element region by applying laser light to the amorphous semiconductor thin film to selectively perform a heating process on the amorphous semiconductor thin film, thereby crystallizing the amorphous semiconductor thin film in a region irradiated with the laser light; and inspecting the crystallinity degree of the crystalline semiconductor thin film. The step of inspecting includes the steps of determining a contrast between the luminance of a crystallized region and the luminance of a non-crystallized region by applying light to the crystalline semiconductor thin film and the amorphous semiconductor thin film, and performing screening of the crystalline semiconductor thin film on the basis of the determined contrast.