When an instruction to execute a color registration adjustment process is given (S1), an image forming apparatus deactivates a sheet feed driving section and a fixing unit (S2), stops communications with external devices (S3), invalidates control sensors excluding an operation section, a door sensor, and sensors involved in formation of images for adjustment (S4), stops a fan (S5), and then executes the color registration adjustment process by forming reference lines and correction lines on a transfer belt and detecting misregistration between them (S6). With this image adjustment method, it is possible to reduce wasteful consumption of developer and efficiently execute the color registration adjustment in a short period of time.