A rear lateral sensing system of a vehicle, comprising: a rear sensing device configured to set a monitoring area in a rear of the vehicle and to detect a rear vehicle in the set monitoring area; a driving determination device configured to catch driving intention of the vehicle and to check whether the vehicle turns and changes lanes; and a controller configured to set the monitoring area with monitoring lines defined based on preset monitoring points, the preset monitoring points being set based on a state in which the host vehicle drives straight ahead, and to reset the monitoring area of the rear sensing device according to a turning angle of the vehicle when the driving determination device confirms that the vehicle turns and changes lanes, further comprising a front sensing device configured to check a road condition in front of the vehicle, wherein the driving determination device is configured to receive information on lanes inputted through the front sensing device and to further check whether the vehicle turns and changes lanes, and characterized in that the controller is further configured to, after the setting of the monitoring area with the monitoring lines defined based on the preset monitoring points, check whether the monitoring area is normally set by setting an arbitrary point (X_Track, Y_Track) on the road corresponding to a lane next to the current driving lane of the vehicle and checking whether the arbitrary point is located in the monitoring area, the arbitrary point being set arbitrarily on the rear lateral side in the lane next to the lane in which the vehicle is located and being set according to a distance between the vehicle and the rear vehicle. a rear sensing device configured to set a monitoring area in a rear of the vehicle and to detect a rear vehicle in the set monitoring area; a driving determination device configured to catch driving intention of the vehicle and to check whether the vehicle turns and changes lanes; and a controller configured to set the monitoring area with monitoring lines defined based on preset monitoring points, the preset monitoring points being set based on a state in which the host vehicle drives straight ahead, and to reset the monitoring area of the rear sensing device according to a turning angle of the vehicle when the driving determination device confirms that the vehicle turns and changes lanes, further comprising a front sensing device configured to check a road condition in front of the vehicle, wherein the driving determination device is configured to receive information on lanes inputted through the front sensing device and to further check whether the vehicle turns and changes lanes, and characterized in that the controller is further configured to, after the setting of the monitoring area with the monitoring lines defined based on the preset monitoring points, check whether the monitoring area is normally set by setting an arbitrary point (X_Track, Y_Track) on the road corresponding to a lane next to the current driving lane of the vehicle and checking whether the arbitrary point is located in the monitoring area, the arbitrary point being set arbitrarily on the rear lateral side in the lane next to the lane in which the vehicle is located and being set according to a distance between the vehicle and the rear vehicle.