A drive cone 11 and a diaphragm 14 are integrally driven by a voice coil 6 movably disposed in a magnetic gap 5. Peripheral edge portions of the drive cone 11 and the diaphragm 14 are supported by a frame 12 via different edge portions 13 and 15, respectively.The drive cone 11 is provided with a rising-up portion 11a which rises up toward an acoustic radiation direction from a inner circumferential end, and a rising-down portion 11b which rises down toward a direction reverse to the acoustic radiation direction. An inner circumferential edge of the diaphragm 14 is fixed at an annular top formed between the rising-up portion and the rising-down portion. Moreover, a first rib 11c and a second rib 11d are formed on the drive cone 11 in such a manner as to rise up toward the acoustic radiation direction integrally with the drive cone. The diaphragm 14 is supported also at the tips of the ribs.