PURPOSE: To provide a fixing device capable of always imparting the heat of an optimum quantity to unfixed toner on a form, without generating the overshooting/undershooting of the surface temperature of a heating roller, caused by the heat conductivity of a rubber layer, and an electrophotographic device using the fixing device.

CONSTITUTION: A heater 103 and a fan 110 are controlled based on the result of the detection of a mean 104 for detecting the inner surface temperature of the rubber layer of the heating roller and a means 102 for detecting its surface temperature. Even if paper does not pass, the same temperature gradient as that when the paper passes, is formed in the rubber layer. Therefore, the proper quantity of accumulated heat in the rubber layer, can be set in advance, before fixing is started, so that the heat of the optimum quantity can be always imparted to the unfixed toner on the paper.