One or two auxiliary rollers of relatively small diameter are pressed against the peripheral surface of a main rotatable body which is heated. Where the two auxiliary rollers are employed, they are spaced apart from each other and are rotated in one direction at the same peripheral speed as that of the main rotatable body. A sheet carrying an unfixed toner image is fed by being gripped between the main rotatable body and the auxiliary rollers, during which the toner is heated and dried, and fixed to the sheet with the solvent evaporated. Thereafter, the sheet is discharged toward a next process. The sheet auxiliary sheets are relatively disposed under certain positional conditions for keeping the sheet in intimate contact with the main rotatable body to achieve proper toner fixing and sheet feeding operations.