A key module, a keyboard and an electronic device using same are provided. The key module includes a substrate, a light receiver, a light emitter and a lifting mechanism. The light receiver is disposed on and electrically connected with the substrate. The light emitter is disposed on and electrically connected with the substrate and disposed opposite to the light receiver. The lifting mechanism is disposed on the substrate and includes an interrupting portion, wherein the interrupting portion is movable to a region between the light receiver and the light emitter.