A speaker includes a diaphragm 11, edges 12, at least one voice coil bobbin 14, a voice coil 15, and a magnetic circuit 21. The diaphragm 11 is a long flat plate. The edges 12 at ends of the diaphragm 11 in a longer-side direction support the diaphragm 11 to vibrate. The voice coil bobbin 14 has a substantially square pillar shape with a height more than twice as vibrational amplitude of the diaphragm 11, includes an opening having a periphery connected directly to the diaphragm 11, and supports the diaphragm 11 to transmit vibration to it. The voice coil 15 is wound around an outer periphery of the voice coil bobbin 14 substantially at center in a height direction. The magnetic circuit 12 drives the voice coil 15. The long speaker is unlikely to cause breakeup resonance, and has smooth frequency characteristics to offer good sound quality.