This inertia sensor is provided with: a first and a second detection unit for respectively outputting a first and a second detection signal; an amplifier having input terminals for selectively inputting the first and second detection signals; a feedback circuit unit configured to be connected in parallel to the amplifier input terminals and output terminal; a first switch element situated between the first detection unit and an input terminal of the amplifier; a second switch element situated between the first detection unit and the feedback circuit unit; a third switch element situated between the first detection unit and an input terminal of the amplifier; and a fourth switch element situated between the second detection unit and the feedback circuit unit. According to this inertia sensor, the output characteristics of the feedback circuit unit are stabilized, and the occurrence of unwanted signals is minimized.