PURPOSE: To provide a loaded-condition detecting device which can instantaneously determine whether or not a temperature detection means is connected, without forcing the temperature of a fixing roller to vary.

CONSTITUTION: The switches of a reference resistance selection means 5 on the side of a first high reference resistance 3 and on the side of a second low reference resistance 4 are alternately made to conduct by a reference resistance selection control means 6, so as to connect each reference resistance to a load 1; potential divided by each reference resistance is detected by means 7 for detecting potential and for detecting loaded conditions, and the detection result is displayed in means 8 for displaying and reporting loaded conditions, and is reported to an external device 9.