An image forming apparatus comprising: a carriage that includes at least one head and is moved for scanning in a main-scanning direction, the head including a black nozzle array (4k2) in which a plurality of nozzles for ejecting black droplets are arranged and a color nozzle array (4cl, 4c2) in which a plurality of nozzles for ejecting color droplets are arranged, the black nozzle array (4k2) being disposed at a position shifted in a sub-scanning direction downstream in a medium conveying direction with respect to the color nozzle array (4cl, 4c2); a conveying unit (13, 14, 16, 17, 18) configured to convey a recording medium in the sub-scanning direction; and a control unit including a CPU that performs overall control of the image forming apparatus, and a ROM which stores a computer program that causes the CPU to perform control concerning carriage movement and droplet injecting in order to form an image by the color nozzle array (4cl, 4c2) in a main scanning in one direction, to perform control concerning sheet conveying in order to relatively move the recording medium to a subsequent main-scanning position thereafter, and to perform control concerning carriage movement and droplet injecting in order to form an image by the black nozzle array (4k2) on the image formed by the color nozzle array (4c1, 4c2) in a following main scanning in the other direction so as to complete an image for one scanning area, wherein the control unit further includes a head driver for driving each of the color nozzle array (4c1, 4c2) and the black nozzle array (4k2), characterized in that the head driver is configured to drive the nozzle arrays in such a manner that the black droplets by the black nozzle array (4k2) are always shot last. a carriage that includes at least one head and is moved for scanning in a main-scanning direction, the head including a black nozzle array (4k2) in which a plurality of nozzles for ejecting black droplets are arranged and a color nozzle array (4cl, 4c2) in which a plurality of nozzles for ejecting color droplets are arranged, the black nozzle array (4k2) being disposed at a position shifted in a sub-scanning direction downstream in a medium conveying direction with respect to the color nozzle array (4cl, 4c2); a conveying unit (13, 14, 16, 17, 18) configured to convey a recording medium in the sub-scanning direction; and a control unit including a CPU that performs overall control of the image forming apparatus, and a ROM which stores a computer program that causes the CPU to perform control concerning carriage movement and droplet injecting in order to form an image by the color nozzle array (4cl, 4c2) in a main scanning in one direction, to perform control concerning sheet conveying in order to relatively move the recording medium to a subsequent main-scanning position thereafter, and to perform control concerning carriage movement and droplet injecting in order to form an image by the black nozzle array (4k2) on the image formed by the color nozzle array (4c1, 4c2) in a following main scanning in the other direction so as to complete an image for one scanning area, wherein the control unit further includes a head driver for driving each of the color nozzle array (4c1, 4c2) and the black nozzle array (4k2), characterized in that the head driver is configured to drive the nozzle arrays in such a manner that the black droplets by the black nozzle array (4k2) are always shot last. to perform control concerning sheet conveying in order to relatively move the recording medium to a subsequent main-scanning position thereafter, and to perform control concerning carriage movement and droplet injecting in order to form an image by the black nozzle array (4k2) on the image formed by the color nozzle array (4c1, 4c2) in a following main scanning in the other direction so as to complete an image for one scanning area, wherein the control unit further includes a head driver for driving each of the color nozzle array (4c1, 4c2) and the black nozzle array (4k2), characterized in that the head driver is configured to drive the nozzle arrays in such a manner that the black droplets by the black nozzle array (4k2) are always shot last.