An inertial sensor includes an oscillator, a drive unit for oscillating the oscillator, a sensor for sensing the amount of inertia applied to the oscillator, and a failure diagnosis unit disposed between the oscillator and the drive unit. The drive unit includes a reference potential supply unit for supplying a reference potential to the oscillator, and a drive signal supply unit for supplying a drive signal to the oscillator based on a monitor signal received from the oscillator. The failure diagnosis unit includes a diagnosis unit for diagnosing a failure based on the value of a current supplied by the reference potential supply unit to the oscillator. The inertial sensor having this structure can detect a failure in the drive unit or the oscillator.