To suppress the meandering of a belt, and to rapidly correct the meandering, if it happened.

The image forming device is provided with the image carrier belt 160 which is stretched to be laid between plural rollers including a tension roller 120 having both end parts 122 formed in a tapered shape so as to be circulatingly driven, and which is provided with beads 161 at both side edge parts on the rear side of the belt, and also, the image forming device is provided with a biasing means 222 for energizing both ends of the tension roller 120 in a belt stretching direction, and the both ends of the tension roller 120 are mutually and independently hung by levers 221, and also, the biasing means is constituted of a common biasing means on both ends.