Provided is an image forming apparatus, including first and second drive portions respectively transmitting a drive force to first and second photosensitive drums, the first and second drive portions each including: a transmission gear rotated by the drive force; an idler gear rotated in mesh with the transmission gear; and a drive gear rotated in mesh with the idler gear. When a meshing angle of the idler gear is an angle from a meshing position between the idler gear and the transmission gear to a meshing position between the idler gear and the drive gear with respect to a rotation center of the idler gear, the meshing angles of the idler gears of the first and second drive portions are substantially equal to each other, and rotational phases of the idler gears of the first and second drive portions match with each other.