A loudspeaker, elongated as viewed from a direction in which sound waves are emitted therefrom, the loudspeaker comprising: an elongated flat-plate-shaped diaphragm; a frame having an opening portion larger than the diaphragm; an edge placed between an inner periphery of the frame around the opening portion and an outer periphery of the diaphragm and supporting and allowing the diaphragm to easily vibrate in an emission direction of the sound waves emitted from the loudspeaker, the diaphragm being elongated in a direction orthogonal to the emission direction; a coupling cone extending from a rear surface of the diaphragm, as viewed from the emission direction of the sound waves, and including two elongated portions arranged parallel to a longitudinal direction of the diaphragm, the coupling cone vibrating in conjunction with the diaphragm; a voice coil wound around at least the two elongated portions of the coupling cone; and a magnetic circuit including: a center pole located in a center portion of the loudspeaker, as viewed from the emission direction of the sound waves; and top plates and magnets located so as to form magnetic gaps with the center pole, as viewed from the emission direction of the sound waves, wherein the magnetic circuit imparts, to the voice coil, a driving force for generating the sound waves, wherein: the voice coil is located within the magnetic gaps formed by the top plates, the magnets and the center pole; a distance between the two elongated portions of the coupling cone is smaller at end positions of the two elongated portions of the coupling cone than at root positions of the two elongated portions of the coupling cone, the end positions being furthest from the rear surface of the diaphragm and the root positions being closest to the rear surface of the diaphragm; the end positions being outwardly located with respect to an outer periphery of the center pole; characterized in that the root positions are inwardly located with respect to an inner periphery of each of the top plates and the magnets. an elongated flat-plate-shaped diaphragm; a frame having an opening portion larger than the diaphragm; an edge placed between an inner periphery of the frame around the opening portion and an outer periphery of the diaphragm and supporting and allowing the diaphragm to easily vibrate in an emission direction of the sound waves emitted from the loudspeaker, the diaphragm being elongated in a direction orthogonal to the emission direction; a coupling cone extending from a rear surface of the diaphragm, as viewed from the emission direction of the sound waves, and including two elongated portions arranged parallel to a longitudinal direction of the diaphragm, the coupling cone vibrating in conjunction with the diaphragm; a voice coil wound around at least the two elongated portions of the coupling cone; and a magnetic circuit including: a center pole located in a center portion of the loudspeaker, as viewed from the emission direction of the sound waves; and top plates and magnets located so as to form magnetic gaps with the center pole, as viewed from the emission direction of the sound waves, wherein the magnetic circuit imparts, to the voice coil, a driving force for generating the sound waves, wherein: a center pole located in a center portion of the loudspeaker, as viewed from the emission direction of the sound waves; and top plates and magnets located so as to form magnetic gaps with the center pole, as viewed from the emission direction of the sound waves, wherein the magnetic circuit imparts, to the voice coil, a driving force for generating the sound waves, wherein: the voice coil is located within the magnetic gaps formed by the top plates, the magnets and the center pole; a distance between the two elongated portions of the coupling cone is smaller at end positions of the two elongated portions of the coupling cone than at root positions of the two elongated portions of the coupling cone, the end positions being furthest from the rear surface of the diaphragm and the root positions being closest to the rear surface of the diaphragm; the end positions being outwardly located with respect to an outer periphery of the center pole; characterized in that the root positions are inwardly located with respect to an inner periphery of each of the top plates and the magnets.