1. A driving action estimating device, comprising: a driver model that describes, with time-series data of N types of characteristic amounts detected during travel of a vehicle as learning data, a probability distribution of existence of the respective data in N dimensional spaces; characteristic amount obtaining means for obtaining at least one or more characteristic amounts from the N types excluding a certain characteristic amount x; maximum posterior probability calculating means for calculating a maximum posterior probability in the driver model for the obtained characteristic amount; and output means for outputting an estimated value of the certain characteristic amount x for the obtained characteristic amount based on the calculated maximum posterior probability.