A detector device includes a drive circuit for outputting a drive pulse signal for displacing the variable block, a detection pulse signal applying unit by which the variable capacitance elements and the fixed capacitance element whose one end is connected in common are respectively applied, at their other ends, with detection pulse signals with a plurality of phases each having a predetermined phase difference at a timing synchronized with the drive pulse signal, and an inertia detection unit for detecting a difference in capacitance value between the variable capacitance elements to which the detection pulse signal having the phase difference is applied, or between the fixed capacitance element and the variable capacitance element, and detecting the applied inertial force based on the difference.