A fixing apparatus includes a tubular film, an elongate heater, a roller, and a lubricant interposed between the heater and the film. A temperature detecting member detects a temperature of the heater, a controller controls electrical power supplied to the heater so that a temperature detected by the temperature detecting member reaches a target temperature, and a guide member guides the film. The guide member has a plurality of protrusions protruding toward the inner surface of the film. In a longitudinal direction of the guide member, a first region of the guide member corresponds to the temperature detecting member, and a second region of the guide member does not correspond to the temperature detecting member. In addition, a width of one protrusion located at the first region is greater than a width of some of the plurality protrusions located at the second region.