In a fixing device for causing a pressurizing roller to come in pressure contact with a heating roller including a central region heating heater for heating a central region and a side end region heating heater for heating a side end region on an outside of the central region, thereby fixing an unfixed toner, or an image forming apparatus comprising the fixing device, an outside of an image region of the heating roller is caused to have a peak of heat distribution of the central region heating heater and heat radiated from both side ends of the heating roller is compensated to flatten the temperature distribution of the image region, thereby preventing a deterioration in an image.