To stop a vehicle in safety furthermore and to detect an error when an acceleration sensor mounted to an electric vehicle fails due to disconnection or the like.

When an output signal from an acceleration sensor 14 varies abruptly, an acceleration sensor value is replaced by a 0 level for a predetermined period T2 and a motor 5 is stopped. An output from the acceleration sensor is monitored even during the period T2 and if it does not vary, the acceleration sensor value is sustained at a 0 level until the period T2 elapses. After the elapse of T2, the output from the acceleration sensor 14 is read in and when a significant variation takes place or the acceleration sensor value returns to a 0 level, the motor 5 is driven to avoid erroneous determination in error detection.