A color image forming apparatus may include photoconductors, developing rollers, and cases, each configured to hold developer to be supplied to a corresponding photoconductor from a corresponding developing roller, and each having an elongated opening in which the developing roller is disposed. Also included are a side seal member disposed at each end of the elongated opening in a longitudinal direction of the opening, each side seal member contacting a peripheral surface of the developing roller at each end of an axial direction of the developing roller, and a belt configured to move in a transporting direction parallel to an arrangement direction of the photoconductors, the belt being disposed below the developing rollers. The belt can be disposed to avoid contacting the photoconductors in an area defined by the side seal members being projected onto a plane on a surface of the belt parallel to an axis of the photoconductors.