A fixing device includes a fixing belt, a distortion detection section that detects distortion in which a magnitude of bending at one side edge in a width direction of a recording medium entering a fixing nip is different from a magnitude of bending at the other side edge in the width direction, a conveying speed changer that changes a conveying speed of the fixing belt in the width direction, and a hardware processor that controls the conveying speed changer such that the conveying speed of the fixing belt in the width direction is changed to eliminate the distortion in a case where the distortion is detected.