Abstract: Whether a driver is driving intentionally is determined rapidly and accurately when steering control is performed such that a vehicle travels along recognized travel partitioning lines. A torque value deviation absolute value is calculated using the absolute value of a difference between the torque value from the previous processing and the torque value from the current processing, and is stored in a ring buffer. A torque value deviation sum value is calculated by adding all the torque value deviation absolute values stored in the ring buffer, and when a state in which the torque value deviation sum value is equal to or less than a predetermined driving intention determination threshold continues for a predetermined first threshold time (for example, several seconds; e.g. 5 seconds) or longer, it is determined that there is a decrease in the driving intention.