To provide an image forming device capable of eliminating the necessity for the enlargement of a space for mounting, and an increase of size of a first image forming part and mounting a second image forming part having a larger capacity than that of the first image forming part in the device.

In the image forming device 10 has the spaces 100 for mounting for mounting or dismounting a plurality of image forming parts 51A-51D each having a standard capacity to form images having various colors different from each other, the image forming device 10 characterized by comprising the image forming parts 1A, 1C having large capacities is constituted by using one of the first space 100A to the fourth space 100D in which the image forming parts 51A-51D having standard capacities are not mounted among the spaces 100 for mounting.