PURPOSE: To embody an acceleration sensor capable of detecting even a low acceleration, and easy in size reduction.

CONSTITUTION: A mass body 3 received within a cylindrical case 4 is guided by the case and moved when an acceleration is generated, one coil spring-shaped elastic body 1 or 2 is elongated, and the other elastic body 2 or 1 is contracted. At this time, a potential difference according to the acceleration is generated between piezoelectric material films 1b and 2b set as mechanical strain/electric characteristics conversion films respectively in both elastic bodies, because both elastic bodies are electrically connected through the mass body 3. The potential difference is outputted from electrodes 7, 8 as acceleration information.