provided are a method of manufacturing a plastic substrate having a tft , a substrate manufactured thereby , a method of manufacturing a flat panel display device , and a flat display device manufactured thereby , which can be used for a flexible flat display device . the method includes : preparing a film in which a plurality of conductive patterns are included ; bonding the film to a substrate ; forming the tft in a manner such that it is electrically connected to the conductive pattern on the film ; and forming an insulating layer covering the tft on the film .