To supply a toner to a development device prior to image formation while suppressing variation in toner concentration.

An image forming system 1 comprises a toner supply amount calculation unit 93 and a drive control unit 31. On the basis of an integration value obtained by integrating the number of pixels in each area in which an image is formed from a toner of each print medium in image data for image formation on a plurality of print media, the toner supply amount calculation unit 93 calculates the total amount of toners required for image formation onto the plurality of print media and calculates each amount obtained by dividing the calculated total amount of toners on the basis of preset division information. Before starting developing images onto the plurality of print media by a developing device 44, the drive control unit 31 controls a drive unit 46 so as to supply toners from a toner bottle 45 to the developing device 44 for each amount calculated by the toner supply amount calculation unit 93.