A transmission mechanism of an image forming apparatus includes: a first transmitting section transmitting a driving force of a drive mechanism to a first transporting roller; and a second transmitting section transmitting the driving force of the first transmitting section to a second transporting roller. The first transmitting section has a first gear rotatable integrally with the first transporting roller. The second transmitting section has a second gear engaged with the first gear; a shaft extended in a direction intersecting the rotational axes of the first and second transporting rollers, and rotatable integrally with the second gear; a third gear rotatable integrally with the shaft; and a fourth gear engaged with the third gear and rotatable integrally with the second transporting roller. The image forming apparatus is capable of transporting a paper favorably along a re-transporting path.