PURPOSE: To provide an image forming device capable of excellently forming an image on the rear of a transfer material on whose surface the image has been formed.

CONSTITUTION: This device is equipped with an image forming part 6 forming the image on the transfer material, and an automatic double-sided device 70 reversing and supplying the transfer material on whose surface the image has been formed to the image forming part. The automatic double-sided device is provided with a paper supplying roller 75a coming in contact with the surface of the transfer material, where the image has been formed, and carrying and supplying the transfer material to an aligning roller pair 78, and the time for driving the paper supplying roller is adjusted by an adjusting mechanism in accordance with the image density of the surface of the transfer material detected by a density sensor.