Fixing device and image forming apparatus

A fixing device comprising:

• a rotatable endless fixing belt;
• and
• an end portion holder which supports each of end portions of the fixing belt rotatably, has a cylindrical part along which an inner circumferential surface of the fixing belt slides and an end wall part which faces an end surface of the fixing belt, and is non-rotatably supported by a fixing frame, wherein
• the end wall part has a restraint part which faces an outer circumferential surface of the fixing belt with a predetermined interval and restrains the fixing belt from turning up,
• the end wall part has a groove along a circumferential direction of the cylindrical part, into which the end portion of the fixing belt can enter,
• the restraint part is an outer circumferential surface of the groove, and
• when the fixing belt is rotated normally, the end portion of the fixing belt does not enter the groove.