A self-diagnostic device for an acceleration or angular-velocity sensor includes a diagnosis control unit, an integration unit, and a determination unit. The diagnosis control unit provides pseudo acceleration or angular velocity to a sensor main body for detecting acceleration or angular velocity, by applying a test signal having prescribed magnitude to the sensor main body. The integration unit integrates a sensor signal outputted from the sensor main body in response to the test signal. The determination unit determines whether or not an integration value obtained at an elapse of prescribed integration time from a time point when the integration unit starts integrating the sensor signal falls within a prescribed normal range.