PURPOSE: To make it possible to perform accurate measurement of gravity by preventing the variation of the wt. suspended from the lower end of a string even if a leaf spring receives temp. influence, by attaching the leaf spring connected to the string to a support in a horizontal direction, and providing a press member in a state contacted with the upper surface of the leading end of the leaf spring.

CONSTITUTION: When a current is flowed to a string 2 having a wt. 4 suspended therefrom, the string 2 is vibrated because the string passes through the magnetic field of a permanent magnet 5. This vibration is led out as an electric signal and, after this signal is amplified by the amplifier of a return circuit, it is again returned to the string 2 to flow a vibration current. Whereupon, the string 2 is self-excited and oscillated at set vibration frequency. By calculating this frequency, gravity acceleration is measured. The leading end of the leaf spring 3 connecting the string 5 is restricted by a press member 7 and the leaf spring 3 is held to a horizontal state within preset temp. change without generating the displacement of the leading end thereof. Therefore, the wt. 4 is always held to a constant position and, as a result, gravity can be accurately measured from the vibration frequency of the string 2.