An automobile beltline portion sound insulating structure formed along a beltline of an automobile, a door panel having two panel boards facing each other, a door glass being freely openable and closable by being provided between the two panel boards in a liftable manner and a first viscoelastic member mounted on a lower portion of at least one main surface of the door glass, the first viscoelastic member constrained by a mounting region of the first viscoelastic member in the door glass and a part of a surface of the panel board facing to the one main surface, at a door glass closed time, to insulate sound between the door panel and the door glass.