A fixing device is provided with a magnetic flux generating unit, first and second rotary bodies, a fixing belt, a temperature sensing portion, a stopped time measuring portion, an abnormality determination portion, and a heating delay portion. The fixing belt extends between the first and second rotary bodies, and is heated by the first rotary body. The temperature sensing portion is disposed downstream of the first rotary body and senses the temperature of the fixing belt. The stopped time measuring portion measures a time period after heating has been stopped before an instruction to start heating is inputted. The abnormality determination portion determines any abnormality in the fixing belt based on a change in temperature after heating has started. When a stopped time is shorter than a pre-configured time period, the heating delay portion delays the start time via magnetic flux based on the instruction to start heating.