A control processor acquires information from an outdoor camera and, from the information, calculates a width W3L of a side strip between a left mark line DL L and a road end E RL . In the case where the width W3L is wider than a specified width, steering torque based on a first steering characteristic CH1 and steering torque based on a second steering characteristic CH2 are exerted. The steering torque based on the first steering characteristic CH1 is exerted in the case where a lateral end of a vehicle is located within a range from a left mark line outer end E DLL to a characteristic switching position P1, and the steering torque based on the second steering characteristic CH2 is exerted in the case where the lateral end of the vehicle is located within a range from the characteristic switching position P1 to the road end E RL . The characteristic switching position PI is set in accordance with the width W3L of the side strip between the left mark line DL L and the road end E RL .