This disclosure depicts a mechanism for guiding movement of a door glass in a motor vehicle door having a door panel, front side door frame, and a rear side door frame that leans forwardly. The mechanism includes a door frame glass guide formed in the front of the rear side frame, for guiding a rear end edge of the door glass in the vertical direction and restraining the rear end edge of the door glass from moving in the direction of the thickness of the door glass. The mechanism also includes a front guide for guiding the forward end portion of the door glass in the vertical direction at least to a predetermined partially opened portion below a beltline portion of the door panel and restraining the door glass from moving in the direction of the thickness of the door glass. The mechanism is constructed such that the door glass is guided parallelly along the rear side door frame within the range from the fully closed position to the predetermined partially opened position and the rear end edge of the door glass is guided in a manner to rock about a bottom end position of the front guide between the partially opened position and a fully opened position.
