To make acoustic sound to be discharged from a loudspeaker device become an ideal cylindrical wave, which has nondirectional characteristic towards the listeners and proceeds in the horizontal direction.

The loudspeaker device is configured such that one end of a vibration transmitting member 2 is supported at an apex A section of a conical diaphragm 1, and vibration in accordance with an acoustic signal is applied to the other end of the vibration transmitting member 2, by a vibrating element 3. The angle θ, between a perpendicular line brought down from the apex A of the conical diaphragm 1 to the bottom face, and the side face of the acoustic diaphragm, is configured such that a range reached by an acoustic sound discharged from the apex A section, and a range reached by an acoustic sound discharged from an end section of the side face that is farthest from the apex becomes equal, based on the speed of sound through air, and the speed of sound within the conical diaphragm 1.