Abstract: An improved structure of magnet type sounder of an electronic acoustic alarm mounted on the engine of a car, wherein primarily, a sound emitting circuit board is placed on an acoustic pipe of a supporting plate, and a magnet is held in a housing formed by an encircling plate beneath the supporting plate, and a sound transmitting case is formed as a flare on the bottom portion thereof which is convex in the inward direction to form a spherical dome surface of which an acoustic pipe column is telescopically placed over the acoustic pipe of the supporting plate, this assembly is then placed in a main case body, and further an acoustic resonant lid covers a through hole of the acoustic pipe column of the sound transmitting case, so that an object of volume reducing can be achieved,