A vehicle door comprises an outer door panel (D2), an inner door panel (D1) formed with an aperture (3) and a plastic mounting panel to which functional devices (30,31,33,70,R.H) of the vehicle door and door parts are installed and which is installed to the inner door panel to close up the aperture of the inner door panel, the mounting panel comprising a plastic panel (P) formed in conformity with the aperture (3) of the inner door panel (D1), a plastic structural part (22,23) appendant to the plastic panel, and a breakable joint connecting the plastic structural part to the plastic panel as one whole piece. The structural part (22,23) is separated from the plastic panel by breaking away the joint from the plastic panel and installed to the plastic panel after having installed the plastic panel to the vehicle door in order to cover up an access opening which provide an access to the interior of the vehicle door for assembling for example an exterior door handle and window glass.