PURPOSE: To improve the measuring accuracy of an absolute-gravity accelerometer applying a Micheloson type laser interferometer by using a dropping body fitted with both of a beam splitter and reflecting mirrors.

CONSTITUTION: The light emitted from a source is led to an interferometer by means of mirrors through a beam splitter above a beam adjuster. The light returned from each reflecting mirror is made incident on a photodetector, by which the light is analyzed after the light is converted into electric signals, through the beam splitter. The light enters and comes out from a vacuum tank through a upper beam splitter. Although longitudinal vibrations are induced to a dropping body when the body is released, only a secondary effect appears in interference signals, since the apparent optical center of a corner cube prism 2 by means of the beam splitter 1 vibrates in the horizontal direction. In other words, the dropping body can be measured when the body drops in a short dropping distance, since the vibrations produced at the time of release do not lower the grade of the signals.