An automatic steering device applies a steering torque in an automatic steering
mode to a steering shaft of a steering mechanism that turns a wheel of a vehicle
in accordance with rotation of the steering shaft connected to a steering wheel.
The automatic steering device includes a controller that calculates an automatic
steering torque value and a target assist torque value, and an actuator that is
controlled by the controller so as to apply torque corresponding to a sum of the
automatic steering torque value and the target assist torque value to the steering
shaft. The controller calculates the target assist torque value by multiplying
an assist torque gain by a steering torque applied by an operator of the vehicle
from the steering wheel to the steering shaft, and sets the assist torque gain
in the automatic steering mode so as to be smaller than an assist torque gain in
a non-automatic steering mode.