A heating device includes a rotatable film, a heater including a substrate that extends along a first direction, and a heater element on the substrate and facing the film, a heat conductor having first and second surfaces and including a first portion contacting the substrate, and a second portion that is adjacent to the first portion in a second direction perpendicular to the first direction and does not contact the substrate, and a temperature sensing element on the second surface at a position corresponding to the second portion. A thickness of the first portion from the first surface to the second surface is greater than a thickness of the second portion from the first surface to the second surface.