A speaker, comprising: a housing including one rectangular main surface, and an opening portion in the one main surface; a diaphragm of a round, elliptical, or track shape disposed in the opening portion, an outer circumference of the diaphragm being surrounded by corner regions of the main surface which are areas at respective vertices of the rectangular main surface; a driving unit for causing the diaphragm to vibrate so as to generate a sound corresponding to a signal inputted from an outside; wherein the driving unit includes a magnetic circuit disposed in the housing; a magnetic gap provided in the magnetic circuit; a voice coil inserted in the magnetic gap and being joined to an outer circumference part of the diaphragm so as to have an annular shape; and a magnetic fluid filled in a gap between the voice coil and the magnetic circuit so as to block sound leakage from the gap; a plurality of movable supports (140a to 140d) disposed in the respective corner regions, for supporting the diaphragm by joining the housing and the diaphragm such that the diaphragm is vibratable; wherein the plurality of movable supports (140a to 140d) each includes: an elastic body (141a to 141d) disposed in a corresponding one of the corner regions so as to have elasticity in directions parallel to one of two sides forming a corresponding one of the vertices of the rectangular shape in the one main surface; and a coupling (142a to 142d) which couples between the elastic body (141a to 141d) and the diaphragm, and which vibrates together with the diaphragm; wherein each of the movable supports (140a to 140d) includes a cross section, perpendicular to the one main surface, being formed in substantially an arc shape, the cross section including a line in a direction extending between the housing side and the diaphragm side. a housing including one rectangular main surface, and an opening portion in the one main surface; a diaphragm of a round, elliptical, or track shape disposed in the opening portion, an outer circumference of the diaphragm being surrounded by corner regions of the main surface which are areas at respective vertices of the rectangular main surface; a driving unit for causing the diaphragm to vibrate so as to generate a sound corresponding to a signal inputted from an outside; wherein the driving unit includes a magnetic circuit disposed in the housing; a magnetic gap provided in the magnetic circuit; a voice coil inserted in the magnetic gap and being joined to an outer circumference part of the diaphragm so as to have an annular shape; and a magnetic fluid filled in a gap between the voice coil and the magnetic circuit so as to block sound leakage from the gap; a plurality of movable supports (140a to 140d) disposed in the respective corner regions, for supporting the diaphragm by joining the housing and the diaphragm such that the diaphragm is vibratable; wherein the plurality of movable supports (140a to 140d) each includes: an elastic body (141a to 141d) disposed in a corresponding one of the corner regions so as to have elasticity in directions parallel to one of two sides forming a corresponding one of the vertices of the rectangular shape in the one main surface; and a coupling (142a to 142d) which couples between the elastic body (141a to 141d) and the diaphragm, and which vibrates together with the diaphragm; wherein each of the movable supports (140a to 140d) includes a cross section, perpendicular to the one main surface, being formed in substantially an arc shape, the cross section including a line in a direction extending between the housing side and the diaphragm side. an elastic body (141a to 141d) disposed in a corresponding one of the corner regions so as to have elasticity in directions parallel to one of two sides forming a corresponding one of the vertices of the rectangular shape in the one main surface; and a coupling (142a to 142d) which couples between the elastic body (141a to 141d) and the diaphragm, and which vibrates together with the diaphragm; wherein each of the movable supports (140a to 140d) includes a cross section, perpendicular to the one main surface, being formed in substantially an arc shape, the cross section including a line in a direction extending between the housing side and the diaphragm side.