An image forming apparatus includes a raster image data generating unit, a halftone image data generating unit, a size control unit, an image forming unit and a flash fixing unit. The raster image data generating unit generates raster image data of a plurality of color components from document data. The halftone image data generating unit generates halftone image data from the raster image data. The size control unit controls minimum halftone dot sizes of the halftone image data. The image forming unit forms color toner images to be fixed on a recording medium using color toners corresponding to the plurality of color components, based on the halftone image data whose minimum halftone dot sizes are controlled by the size control unit. The flash fixing unit emits flash light from a flash light source to the recording medium to fix the color toner images transferred onto the recording medium.