A fixing device includes: a fixing roller; a support roller arranged apart from the fixing roller; an endless fixing belt wound around the fixing roller and the support roller; a pressing roller for applying a pressure force to the fixing roller while the fixing belt being sandwiched between the fixing roller and the pressing roller; a nip extending member arranged on an upstream of the fixing roller and on an inner side of the fixing belt and having a pressing surface for pressing the fixing belt; and a variable mechanism for changing a state of a pressure applied to the fixing belt by the nip extending member.