a fixing device is provided , which has a fixing roller and a sheet . the recording paper where the toner image has been transcribed thereon is passed through a nip portion between the fixing roller and the sheet . by pressing and heating , the toner image is fixed on the recording paper . a heating line is wound on a surface opposite to a sheet &# 39 ; s surface that is in contact with the fixing roller . by applying a power source to the heating line , the sheet is heated . when the recording paper enters the nip , the cause of the temperature suddenly lowering can be prevented .