The fixing device of the image forming apparatus of the present invention
is provided with a heat transfer probe which contacts the heat roller and
a surface temperature of the heat roller is transferred thereto. The
erroneous detection of the surface temperature of the heat roller caused
from materials adhered to the heat roller is prevented, induction heating
coils is regulated at a high level of accuracy using the highly precious
detection result obtained from the heat transfer probe, the temperature
control of the heat roller is promoted and a fixed image of high quality
is obtained.