Abstract: A hybrid type image forming apparatus capable of forming a high quality image by using two image forming units having different resolution from each other, perform high throughput image forming by selecting most suitable image forming method or methods depending upon a kind of input image data, and reducing its running cost. In the apparatus, input image data of resolution of 300 dpi is separated into monochromatic image data and color image data. The monochromatic image data is converted into that of 600 dpi so that four pixels of an image of 600 dpi make one pixel of an image of 300 dpi. Then, a monochromatic image is formed on the basis of the monochromatic image data of 600 dpi by the image forming unit employing the electrophotograph method. A print medium on which the monochromatic image is formed is conveyed to the image forming unit employing the ink-jet printing method where a color image is formed on the basis of the color image data of 300 dpi.