A car door structure comprises a door inner panel 11, an interior door trim 12 and a noise insulation sheet 20. The interior door trim 12 is installed in the interior side of the door inner panel 11. The noise insulation sheet 20 is provided between the door inner panel 11 and the door trim 12, where it is hung down from the upper side to the lower side of the door inner panel like a curtain. The noise insulation sheet 20 is fixed to either the door inner panel 11 or the door trim 12. The noise insulation sheet 20 is provided at about an upper half or a lower half of the door inner panel 11, or it is provided at a central part of the door inner panel 11 while dividing approximately into three sections in a vertical direction or a horizontal direction.