Drive transmission device (10) includes rotatable member (20), driven member (30), driving coupling (21), and driven coupling (31). Both driving protrusions (22) and driven protrusions (32) are arranged at equal intervals in rotation direction (R). Each driving protrusion (22) is in mating contact with corresponding one of driven protrusions (32). Surface (41) of the driving protrusion (22) that is in contact with the driven protrusion (32) includes inner contact region (42) and outer contact region (43). Inner contact region (42) is located at an inner side relative to planned line (LG) of centroid shift extending in rotation direction (R) through centroid (G) of the driving protrusion (22). Outer contact region (43) is located at an outer side relative to planned line (LG) of centroid shift. Along rotation direction (R), each of the inner contact region (42) and the outer contact region (43) extends toward planned line (LG) of centroid shift.