A metal plate (14) is buried in a gasket (12) of a case (10) for accommodating an electric device such as an inverter. The metal plate (14) is connected to a control board (400) in the case (10), and the voltage of the metal plate (14) is determined. A reference voltage is applied to the metal plate (14), and the case (10) is grounded. When the metal plate (14) is brought into contact with the case (10) or disconnected due to a crash, the voltage of the metal plate (14) is thereby changed, and the control board (400) detects a crash, based on the change in the voltage.