A drive transmission mechanism which transmits a rotational driving force to a roller to be shifted in directions of a rotational axis thereof is equipped with a rotary drive transmission member which is driven to rotate in a predetermined rotational direction, a holder which holds the roller in such a manner that the roller can slide freely in the rotational axis directions while rotating about the rotational axis, and a one-way clutch interposed between the rotary drive transmission member and the holder. The one-way clutch is configured to transmit a rotational driving force from the rotary drive transmission member to the holder, and also to permit the holder to rotate in the predetermined rotational direction relative to the rotary drive transmission member.