A drive unit for a movable member includes the movable member adjusting aerodynamic characteristics of a vehicle while the movable member is changing a position thereof, an electric motor operating the movable member, a preventing device preventing the movable member from operating beyond a specified operating range by making contact with the movable member, and a controlling device supplying an electric power to the electric motor for a reference time and operating the movable member from a first end to a second end of the specified operating range, the controlling device correcting the reference time on the basis of an external factor that affects an operating speed of the movable member.