To detect a quantitative amount corresponding to a human sense load amount in a drive operation situation, in every short time interval.

A steering angle steered by a driver is detected by a steering angle sensor 12, a manipulated variable when execution of a smooth operation is assumed is estimated by a manipulated variable estimating means 22 based on the steering angle detected by the sensor 12, an operational deviation amount between a manipulated variavle estimated value estimated by the an operational deviation amount detecting means 24 and a steering angle detected value is detected, and an operational situation index value is detected by an operational situation index value detecting means 26, based on a waveform when the manipulated variable of the operational deviation amount is detected.