Lane change support device

The lane change support device is configured to estimate a lane speed of another vehicle traveling on a lane of a lane change destination, determine a minimum length of a space in a lane of a lane change destination necessary for lane change based on a lane speed of the other vehicle, estimate an actual length of a space in the lane of the lane change destination, and determine whether lane change is possible based on the minimum length and the actual length, and calculate a target relative speed of the own vehicle with respect to the other vehicle based on an allowable acceleration or deceleration speed of the own vehicle, and search for a space in a lane of a lane change destination necessary for lane change while controlling a vehicle speed of the own vehicle in such a manner that a relative speed becomes a target relative speed.