To eliminate necessity for applying particular molding work to a sealing cover, so that it can be easily surely stuck, attain improvement of seal property between an in-door main body and an in-car and rigidity of a door inner panel.

In a sealing cover mounting structure, in a central position in a vertical direction of a door inner panel 3, a plurality of protruded parts 11 protruding toward a car inner side is arranged with a space apart in a longitudinal direction, in a peripheral surface in a car inner side of the door inner panel 3 and an upper surface of the protruded part 11, a butyl tape of bonding material is respectively mounted, by sticking a sealing cover 10 to the butyl tape, the sealing cover 10 is mounted in the door inner panel 3.