An acceleration sensor having a sensitivity capable of well detecting vibration and an increased impact resistance and outputting acceleration detection signals based on a variation in capacitance between a fixed electrode and a diaphragm (3). The diaphragm (3) is dividedly formed in a vibration part (33) positioned at its center part, a fixed part (31) positioned at its peripheral part, and elastic support parts (32) connecting the vibration part (33) to the fixed part (31) by a plurality of slits (11) formed therein at equal intervals along the circumferential direction. The plurality of support parts (32) having narrow center parts (32c) are circumferentially formed in the diaphragm at equal intervals. Each of the slits (11) is formed so that the end part the vibration part (33) side of the other slit (11) adjacent to one side of the slit in the circumferential direction and the end part of the fixed part (31) side of the other slit adjacent the other side thereof in the circumferential direction can be radially overlapped with each other in a specified district at the circumferential center part thereof.
