A foldable electronic device includes a first base, a second base, a hinge, a brake, an object sensor, and a controller. The hinge pivotally connects the first base to the second base. The brake is disposed in the hinge. When the first base is expanded with respect to the second base, the object sensor senses whether an object is placed on the second base. When the object sensor senses that the object is placed on the second base, the object sensor sends out a sensed signal. The controller selectively switches on the brake in response to the sensed signal, so as to restrain a rotating angle formed by the first base and the second base.