To surely actuate a plurality of power sources.

This passive safety device comprises: a common line; a plurality of power supplies; a plurality of power supply switches each of which connects at least a part of each of the plural power supplies to the common line; the plural power sources whose ends which are not grounded are connected to the common line; a plurality of ignition switches each of which ground each of the plural power sources; a diagnosis means for diagnosing the plural power supplies and the plural power supply switches; and a control means which successively controls the plural power supply switches and the plural ignition switches, and successively supplies the plural power sources with the power supply preferably from the normal power supply and from a pair of the normal power supply and the normal power supply switch based on a diagnosis result by the diagnosis means, thereby successively igniting the plural power sources.