PURPOSE: To make it possible to measure minute acceleration with high accuracy by a simple structure without hermetically closing an apparatus, by providing a groove part to a leaf spring to weaken spring rigidity and filling the groove part with a viscous material.

CONSTITUTION: A base 4 having a coil 3 mounted thereto is suspended from an outer frame 1 by two leaf springs 2 having high rigidity and a pendulum is constituted of the coil 3, the base 4 and the leaf springs 2. A part of each leaf spring 2 is thinly shaved from both sides so that the thickness thereof is reduced to the limit to be formed into groove parts 11 to form a flexural part 12 and extremely reduced in its spring rigidity. The groove parts 11 are filled with a viscous material such as grease. A magnetic path plate 5 and permanent magnets 6a, 6b are respectively arranged to the upper and lower sides of the coil 3 and the base 4. If the direction and magnitude of the current made to flow to the coil 3 are controlled and the pendulum is moved to input the beam from a floodlight projector 9 to the predetermined position of a displacement measuring device 10, acceleration is calculated by a zero method. Because the groove parts 11 of the leaf spring 2 are filled with the viscous material 13, it allows the whole of the pendulum not to enter the viscous material.