This invention relates to a wire-free sensing apparatus used in a disc system. The apparatus mainly comprises a beam emitting source installed at the case for emitting a beam, a reflector installed at the drawer for reflecting the beam, a beam receiving end installed at the case for receiving the beam reflected by the reflector, a switch installed at the drawer for controlling whether the reflector reflects the beam or not, and a one-way mirror installed at the case. The one-way mirror forms a non-right angle with an emitting direction of the beam and has a penetrating surface and a reflecting surface at opposite sides thereof wherein the beam penetrates the penetrating surface, and can be reflected by the reflector to the reflecting surface and then reflected by the reflecting surface to the beam receiving end.