The invention provides a fixing device having at least: a first rotary body, having a heat generating layer from which heat is generated by action of a magnetic field: a second rotary body contacting the first rotary body; a magnetic field generating unit arranged to have a predetermined separation from the inner circumferential face of the first rotary body or to have a predetermined separation from the outer circumferential face of the first rotary body; and a heat generation controlling member arranged facing the magnetic field generating unit, with the first rotary body being between the heat generation controlling member and the magnetic field generating unit, the heat generation controlling member having at least a temperature-sensitive magnetic material having a Curie temperature and controlling generation of heat of the heat generating layer. The invention further provides an image forming device having at least the mixing device.