A loudspeaker, comprising: a frame; a yoke fixed to the frame; a magnet fixed to the yoke; a plate fixed to a first surface of the magnet, the first surface being opposite to a second surface of the magnet which is fixed to the yoke; a voice coil arranged, in a vibratable manner, in a first magnetic gap formed between the yoke and the plate; a diaphragm having a dome shape and an outer edge portion joined to the voice coil; a support member which supports the diaphragm in a vibratable manner, and is composed of a plurality of edges (108a-108d), one end of each edge (108a-108d) being fixed to the frame, and a magnetic fluid disposed between the plate and the voice coil, wherein the plate is composed of a flat-plate part which is fixed to the first surface of the magnet, and has, at a surface opposite the magnet, a planar portion extending from an outer edge of the flat-plate part inwardly up to a predetermined distance, and a protruding part which is disposed on the surface opposite the magnet of the flat-plate part excluding the planar portion, and protrudes toward the diaphragm, and a through-hole is formed so as to penetrate through the yoke, the magnet, and the plate, the through-hole connecting a space outside the loudspeaker with a space on a back surface of the diaphragm, the protruding part extending into the through-hole so as to fix the yoke, the magnet, and the plate, an end of the protruding part on the flat-plate part side being in a dome shape substantially the same as to that of the diaphragm, thereby reducing the volume of the space between the diaphragm and the plate, and an air flow path is provided so as to penetrate through the protruding part along the flat-plate part. a frame; a yoke fixed to the frame; a magnet fixed to the yoke; a plate fixed to a first surface of the magnet, the first surface being opposite to a second surface of the magnet which is fixed to the yoke; a voice coil arranged, in a vibratable manner, in a first magnetic gap formed between the yoke and the plate; a diaphragm having a dome shape and an outer edge portion joined to the voice coil; a support member which supports the diaphragm in a vibratable manner, and is composed of a plurality of edges (108a-108d), one end of each edge (108a-108d) being fixed to the frame, and a magnetic fluid disposed between the plate and the voice coil, wherein the plate is composed of a flat-plate part which is fixed to the first surface of the magnet, and has, at a surface opposite the magnet, a planar portion extending from an outer edge of the flat-plate part inwardly up to a predetermined distance, and a protruding part which is disposed on the surface opposite the magnet of the flat-plate part excluding the planar portion, and protrudes toward the diaphragm, and a flat-plate part which is fixed to the first surface of the magnet, and has, at a surface opposite the magnet, a planar portion extending from an outer edge of the flat-plate part inwardly up to a predetermined distance, and a protruding part which is disposed on the surface opposite the magnet of the flat-plate part excluding the planar portion, and protrudes toward the diaphragm, and a through-hole is formed so as to penetrate through the yoke, the magnet, and the plate, the through-hole connecting a space outside the loudspeaker with a space on a back surface of the diaphragm, the protruding part extending into the through-hole so as to fix the yoke, the magnet, and the plate, an end of the protruding part on the flat-plate part side being in a dome shape substantially the same as to that of the diaphragm, thereby reducing the volume of the space between the diaphragm and the plate, and an air flow path is provided so as to penetrate through the protruding part along the flat-plate part.