An image fixing device including a cylindrical film, a heater, and a heat conduction member. The cylindrical film is contactable with toner unfixed on a sheet. The heater includes a substrate and a heat generating resistor provided on the substrate. The heat conduction member has a thermal conductivity higher than that of the substrate and is on a side of the substrate opposite from the heat generating resistor. The substrate is provided with non-insulating wiring patterns on a side opposite from the side provided with the heat generating resistor with respect to a direction perpendicular to a recording material feeding direction. The heat conduction member is in contact with one of the wiring patterns and is in contact with the substrate from a position of the substrate outside of an end of the heat generating resistor toward a central portion.