An image-fixing method for heat-fixing a toner image, by feeding an transfer medium carrying the toner image between a heating unit heated by an induction-heating process and a pressurizing unit placed to press against the heating unit, wherein the electric resistivity at least of the outermost layer of the heating unit is 10−7 Ωm or more and less than 10−2 Ωm, and the toner image is formed by using a toner containing an amorphous resin having an ionic concentration in the range of 10−5 to 10−3 mole/g as the binder resin.