Provided is a fixing device including a pair of end deformation restraint members. A restraint body 35 of the end deformation restraint member has an insertion part 38 which is inserted into both end portions of a fixing belt, and restrains deformation of belt end portions by holding both end portions of the fixing belt, which slides on an outer peripheral surface of the insertion part 38, from inside in the insertion part 38. The insertion part 38 is continued in a belt rotation direction with no gap.