1. An image forming apparatus, comprising: a first image forming part that forms a first developer image representing an image by using a first developer; and a second image forming part that forms a second developer image serving as a base or covering of the first developer image by using a second developer, wherein in a case where the first developer image and the second developer image are superimposed and formed on an image-formed body by the first image forming part and the second image forming part, amount of the first developer that is used to form the first developer image is increased as compared to a case where the first developer image is formed on the image-formed body by the first image forming part without being superimposed with the second developer image.