PURPOSE: To set the target value of an image density controller with high accuracy in a short time by disposing a reference density member for detecting the density of a reference toner image when an image is not formed by an image forming device and deciding the density control target value based on the density detected value of the reference density member.

CONSTITUTION: In this image forming device, the image is formed by directly forming a toner image on a transfer material carried on an endless carrier 1 which is driven to be rotated or the carrier 1, and the reference toner image 2 is formed on the carrier 1 which is driven to be rotated and the density of the reference toner image 2 is detected by a density detection means 3, then an image forming condition is controlled so that the detected value may be equal to the density control target value previously set. Namely, the reference density member 4 capable of detection by using the detection means 3 detecting the density of the reference toner image 2 formed on the carrier 1 when the image is not formed by the image forming device is disposed and the density control target value is decided based on the detected value of the density member 4 by using the detection means 3 by a control means 5.