There is provided a drive transmission device including: a belt member, a tension applying roller, a holder, an urging member, and a fastening member, wherein the holder includes: a contacting surface that is brought into contact with the fastening member in the case where the holder is fastened to the target member; and a raised portion that has a portion that is brought into contact with the fastening member earlier than the contacting surface in the case where the holder is fastened to the target member, the raised portion being provided on a side of an end portion of the hole in the tension adjusting direction, and the portion of the raised portion that is brought into contact with the fastening member is deformed by being pressed by the fastening member, and becomes a part of the contacting surface in the case where fastening is completed.