A drive transmission unit includes a cam member, a motor, a cam follower, and an extension spring. The cam member rotates about a rotation shaft. The cam member includes a first cam defining a maximum distance between the cam follower and the rotation shaft and a second cam having an outer peripheral surface positioned closer to the rotation shaft than the outer peripheral surface of the first cam. The motor rotates the rotation shaft. The cam follower is to be in contact with the cam member and moves in the +B direction and the −B direction by the rotation of the cam member. The extension spring presses the cam follower against the cam member. When the cam follower moves in the −B direction by the rotation of the cam member, this operation includes contact between the outer peripheral surface of the second cam and the cam follower.