a monitor for monitoring a human condition of a driver, and

an awakening device for making the driver recover a wakeful state or awakening state by starting operation when received a predictive signal for fall-asleep from said monitor, the predictive signal for fall-asleep being a signal when an energy metabolism makes transition from an active state into a sleep state,

a bio-signal peak value detection means for detecting a peak value for each cycle of an original waveform of the bio-signal data;

a power value calculation means for calculating a difference between the peak value at an upper limit side and the peak value at a lower limit side for each certain time range using respective peak values obtained by said bio-signal peak value detection means to thereby set the difference as a power value;

a gradient calculation means for obtaining a gradient of the power value with regard to time base in a certain time range by performing slide calculation the prescribed number of times at a prescribed overlap rate with regard to the prescribed time;

a comparative determination means for comparatively determining whether a sudden drop state of the gradient of the power value exists or not in time-series change in the gradient of the power value obtained by performing slide calculation with said gradient calculation means to thereby determine a time range in which the sudden drop state appears to be the predictive signal for fall-asleep from the active state into the sleep state; and

an output means for outputting the predictive signal for fall-asleep from the active state to the sleep state detected by said comparative determination means.