Abstract: A vehicle constant speed travel control method and device are provided in which a target driving power is calculated based on a difference between a target vehicle speed and a vehicle speed, and then a target accelerator pedal opening for calculating a gear ratio in constant speed travel control is set based on the target driving power. Then, a target gear ratio based on the target accelerator pedal opening and based on a towing state of the vehicle is set where the target gear ratio set higher during towing than during non-towing. The setting of the target accelerator pedal opening is set differently in accordance with the towing state of the vehicle. The setting of the target accelerator pedal opening for calculating the gear ratio to be smaller during towing than the during non-towing with respect to the same target driving power.