PURPOSE: To secure the perpendicularity of a gravity sensor without increasing the gravity of a gravimeter by deciding whether or not the gravimeter body slants from the perpendicular when it reaches the bottom of the sea, and vibrating the gravimeter body and correcting its attitude.

CONSTITUTION: The gravimeter body 3 constituted by providing a ball gimbals 5 which rolls in contact with the internal surface of a case 2 having a spherical internal surface in the case 2 is put in the case 2 so that it can slant. The gravimeter body 3 has the gravity sensor 19 suspended internally through a gimblas mechanism 13 in an oscillatory state and the gravity sensor 19 is fixed by a clamping mechanism 21. The output signal of the gravity sensor 19 is supplied to a measurement control circuit including a microcomputer to measure a gravity value. Then, when the gravimeter reaches the bottom of the sea, the clamp 21 is released and the inclination of the gravity sensor from the perpendicular direction is checked through the specific arithmetic of the microcomputer; when the inclination exceeds a specific value, the clamping mechanism 21 is driven several times to vibrate the main body 3, which is returned to the perpendicular attitude.