PURPOSE: To produce a large acoustic output with simple constitution by using a laminated ceramic as an object for driving the vibration and connecting it to a vibration displacement magnification device.

CONSTITUTION: A vibration drive element 8 made of thin film-like ceramic materials is connected to one edge of a vibration displacement magnification device 9 on the amplitude surface where the vibration displacement is maximized. The device 9 is constituted of a metallic vibration body 10 made of fine bars or thin sheet pieces and a vibration transmission support mechanism 11. Insulating oils 14 for balancing pressure are filled in a sound wave transmitter case 15 for containing said vibration body 10 and mechanism 11 in order to prevent breakage of each connection surface caused by hydraulic pressure applied to a sound wave radiation body 2. With this constitutuion, when the element 9 is driven by low frequency, the sound wave whose vibration displacement is mangified to the prescribed vibration displacement magnification ratio is radiated from the radiator 2, and efficiently emitted underwater through a diaphragm 13.