An input device that inputs a failure signal of a flat panel display in which a failure is found in a process of inspecting flat panel displays of a mother substrate state is provided. The input device includes an input unit that is positioned in the front of a mother substrate and spaced apart from the mother substrate and that has a plurality of labels in which a kind of a failure is written and at least one selection button to generate a failure selection signal, a guide unit that includes a first guide rail that guides horizontal movement of the input unit and a second guide rail that guides vertical movement of the input unit, a position detector that detects a position of the input unit to generate a position signal, and a controller that receives a failure selection signal from the input unit and receives a position signal from the position detector to map failure information of the mother substrate.