An image forming apparatus is provided having a mechanism that toner density of a toner image is automatically adjusted based on a toner patch. In an image forming apparatus including a document conveying section, a document reading section, an image forming section, a sheet discharging section, a sheet feeding section, a patch density detecting section, and a toner density adjusting section for adjusting density of a toner image depending on a result detected by the patch density detecting section, there are further provided a patch forming section for forming a toner patch, an operation detecting section for detecting an operating state of the patch density detecting section, and a patch printing section for printing the toner patch in response to such a result detected by the operation detecting section that the patch density detecting section does not properly operate, thereby adjusting the toner density based on the patch image.