A drive force transmitting mechanism includes a first gear rotatably supported by a first shaft element, a first gear holding unit including the first shaft element and a first support element supporting the first shaft element, a second gear rotatably supported by a second shaft element, a second gear holding unit including the second shaft element and a second support element supporting the second shaft element. The second gear holding unit moves relative to the first gear holding unit, to thereby contact and separate the second gear with and from the first gear. A drive force is transmitted from the first gear to the second gear engaged therewith. A movement of the second gear is regulated by abutting the second shaft element against a curved surface of the first support element that curves at a predetermined curvature relative to an axis line of the first shaft element.