To prevent a sensor from receiving physical damage easily when an excessive outer force is applied.
A doughnut shaped groove is dug on the lower surface of a first substrate 100 and a flexible part is formed. An annular pedestal 220 is joined to the lower surface of a fixed part being located around the donut groove, and a weight body 210 is joined to an operation part that is located inside the donut groove. A second substrate 400 is joined to the upper part of the first substrate 100, electrodes El and E2 are formed at a surface that opposes both substrates 100 and 400, and a capacitance element is formed. A third substrate 300 is joined to the lower surface of the pedestal 220. The weight body 210 is suspended in the air and is displaced when being accelerated. The displacement causes the interval between the electrodes E1 and E2 to change, thus detecting acceleration as the change of capacitance. The first substrate 100, the pedestal 220, and the third substrate 300 exist in the upper direction of the weight body 210, in horizontal direction, and in the lower direction, respectively, thus controlling an excessive displacement and preventing the flexible part from being damaged.