A sealing structure for an automobile door includes a roll sash with a projection on an inner-cabin side surface of an upper end periphery thereof, a press sash without a projection and joined to the roll sash, and a decorative molding which covers the sashes. An installation base member of a weather strip is configured to operably couple to an outer circumferential edge on an upper side of the door sash. The weather strip includes a hollow seal member and an outer seal lip. An outer-cabin side end of the installation base member and a rib-shaped protrusion which extends outwardly toward an exterior of an automobile are configured to clasp the projection. An upper part protrusion which extends outwardly toward the exterior of the automobile from an upper side relative to the rib-shaped protrusion is configured to make close contact with an upper part of the decorative molding.