An image forming apparatus includes the following. An image carrier carries a toner image. A transfer unit transfers a toner image held by the image carrier onto a sheet. A controller controls a relation of a position between the image carrier and the sheet so that the sheet continues to come into contact with the image carrier from a position where a distance from a transfer nip is within a predetermined range when the sheet enters the transfer nip during an image forming job. The transfer nip is formed by the image carrier and the transfer unit.

An optical scanning device includes a rotating polygon mirror, a light source that irradiates first and second light beams at one side of the rotating polygon mirror and irradiates third and fourth light beams at the other side thereof, a first optical element that reflects the first light beam and allows the second light beam to pass therethrough, a second optical element that reflects the second light beam, a third optical element that allows the third and fourth light beams to pass therethrough, and a fourth optical element that reflects the fourth light beam. The second light beam is a light beam corresponding to yellow, the first, the third, and the fourth light beams are light beams corresponding to three colors other than the yellow. Between the third and fourth optical elements, a scanning lens is arranged. Between the first and second optical elements, a scanning lens is not arranged.

In an image forming mode, in which a first image forming portion forms a toner image on a first image bearing member and a second image forming portion does not form a toner image on a second image bearing member, thereby forming an image on a recording material, a first voltage lower than a minimum value of absolute values of a plurality of voltages applied to a plurality of grid electrodes of the first image forming portion and higher than an absolute value of a target potential of a surface of the second image bearing member in the image forming mode is applied to one of a plurality of grid electrodes of the second image forming portion, and no voltage is applied to the other grid electrodes except the grid electrode to which the first voltage is applied among the plurality of grid electrodes of the second image forming portion.

An intermediate transfer unit includes a seamless intermediate transfer belt, a plurality of primary transfer members and a power supply line. On the intermediate transfer belt, toner images formed on a plurality of image carrying members are sequentially stacked. The primary transfer members are respectively arranged opposite the image carrying members via the intermediate transfer belt, and transfer the toner images formed on the image carrying members onto the intermediate transfer belt. The power supply line branches to at least two or more locations from a transfer voltage power supply which applies a primary transfer voltage to each of the primary transfer members to cause a primary transfer current to flow to each of the primary transfer members. The power supply line and each of the primary transfer members are connected via a high-voltage resistor unit that includes a plurality of resistors having different resistance values.