To provide a cover structure for a door opening/closing device covering a space between a door reached to an open position and a vehicle body side wall and the front side and the upper side of the opening/closing device arranged in the space and capable of attaining the enhancement of safety and beautiful appearance.

The cover structure for the door opening/closing device includes: the door opening/closing device 19 for connecting a rear door 4 and a mounting base part 15 on a vehicle body side and for moving the door between a closure position D1 and a projection position D2 on an outer side in a vehicle width direction than the position; a side cover 75 pivotally supported on the vehicle body swingably around a vertical central line Lh, overlapped on a cabin inner surface of a door trim 80 when the door reaches to the closure position and covering the door opening/closing device swingably around the vertical central line Lh, from a side, when the door reaches to the projection position; and an upper cover 754 extended from the side cover, overlapped on an upward surface of a belt line position of the door trim 80 when the door reaches to the closure position D1, and covering the door opening/closing device from above when the door reaches to the projection position D2.