A lane change support device includes a control unit configured to execute lane change control for enabling a vehicle to automatically change lanes from a lane in which the vehicle is traveling to an adjacent lane. The control unit counts a holding time for which an operation part that is operated to a predetermined operation position to start the lane change control is continuously held at the operation position, starts the lane change control when the counted holding time reaches a predetermined threshold time, and calculates a proficiency level of a driver of the vehicle for an operation of the lane change support device during execution of the lane change control and sets the threshold time to be used for a successive lane change control based on the proficiency level.