To provide a belt conveying device, a fixing device and an image forming apparatus which can prevent deflection of a fixing belt in an axial direction of a roller and can prevent wear and damage of a fixing belt.

A fixing belt 70 comprises at least a fixing belt 73 stretched between a heating roller 71 and a fixing roller 72 and is controlled by CPU 201. Sensors 761 and 762, which detect that the fixing belt 73 is deflected in the axial direction of a heating roller 71, are oppositely arranged on both end part sides of the heating roller 71. Ducts 771 and 772, which have cooling parts 781 and 782 respectively, are oppositely arranged on both end part sides of a pressure roller 74. When CPU 201 detects the deflection direction of the fixing belt 73 by the sensors 761 and 762, CPU 201 drives a cooling part disposed on the downstream side in the deflection direction of the cooling parts 781 and 782.