A heating unit includes a first rotatable member that generates heat; a second rotatable member that forms, in combination with the first rotatable member, a nip area through which sheets of different sizes pass one by one; a housing that supports the first and second rotatable members such that the first and second rotatable members are rotatable; an electronic component that is fixed to the housing and includes a portion that overlaps a smallest one of the sheets passing through the nip area in terms of a position in a long-side direction of the nip area; and an other member that is provided between the first rotatable member and the electronic component.