DRIVING STATE ESTIMATION DEVICE

The driving assistance unit acquires distribution data (a steering angle prediction error (¸e)) for the traveling state distributions (a first traveling state distribution, a second traveling state distribution). Next the driving assistance unit converts value of the distribution data (a steering angle prediction error (¸e)) into their absolute values. Next, the driving assistance unit classify the absolute value of the distribution data (a steering angle prediction error (¸e)) in different time ranges into bins as plural segmented data ranges, based on the distribution data (a steering angle prediction error (¸e)) whose values are converted into their absolute values and calculates a frequency distributions of the distribution data (a steering angle prediction error (¸e)) as plural traveling state distributions (the first traveling state distribution, the second traveling state distribution). Next, the driving assistance unit estimates (determines driving instability degree) a driving state of a driver based on the plural calculated traveling state distributions.