Provided is an apparatus for manufacturing a polysilicon thin film by depositing an amorphous silicon thin film and an upper silicon dioxide substrate on a lower silicon dioxide substrate, forming a conductive thin film on the upper silicon dioxide substrate, and applying an electric field and performing Joule heating to crystallize the amorphous silicon thin film, the apparatus comprising power terminals for elastically contacting both upper ends of the conductive thin film and supplying power to the conductive thin film, and support members for elastically supporting the substrate such that the power terminals closely contact both upper ends of the conductive thin film to form a uniform electric field at the conductive thin film. Therefore, it is possible to apply an electric field to a conductive thin film and perform Joule heating to crystallize an amorphous silicon thin film, and support members are installed at both lower surfaces of a silicon dioxide substrate to elastically support the silicon dioxide substrate such that power terminals closely contact both upper ends of the conductive thin film, thereby forming a uniform electric field at the conductive thin film to efficiently perform crystallization within a short time.