Provided is an underwater magnetrostrictive vibration device with reduced signal attenuation and improved in efficiency and sound quality, which has been low due to external noise disturbance. The underwater magnetrostrictive vibration device comprises a watertight vessel, a magnetic circuit constructing member for constructing a closed magnetic circuit having an end inserted watertight in the watertight vessel, a vibrator made of magnetrostrictive alloy and provided in the closed magnetic circuit, a permanent magnet provided in the closed magnetic circuit, for applying a magnetic bias to the vibrator, at least one coil provided in the periphery of the vibrator and selected from the group consisting of a magnetic field generating coil and a magnetic field detecting coil, stress applying means provided in the closed magnetic circuit, for applying compressive force in a vibration direction of the vibrator, a movable member capable of moving in a vibration direction of the vibrator and inserted watertight in an end portion of the magnetic circuit constructing member positioned on the opposite side of the watertight vessel, and a signal processing circuit board provided in the watertight vessel and connected to the at least one coil, for processing at least one signal selected from the group consisting of a vibration-generating signal and a vibration-detecting signal.