Fixing unit and image forming apparatus

A fixing unit comprising:

• a rotary member having a cylindrical shape;
• a pressure member configured to form a fixing nip that fixes a toner image onto a sheet together with the rotary member,
• a heater disposed in an internal space of the rotary member, the heater including a substrate, and a heating element provided on the substrate and configured to heat the rotary member by being energized;
• a heater holder configured to hold the heater;
• and
• a heat conducting member disposed between the heater and the heater holder,
• wherein the fixing nip conveys the sheet in a direction parallel to a short direction perpendicular to a longitudinal direction of the heater,
• the heater includes a protrusion extending toward the heater holder from a surface, of the heater, provided on a side opposite to the fixing nip, and
• the protrusion faces the heat conducting member in the longitudinal direction and is disposed so as not to overlap the heat conducting member as viewed in the short direction.