To resolve a trouble caused due to the temperature increase phenomenon in a part where paper is not passed by moderating the temperature increase phenomenon in such part as much as possible.

This heating body assembly 1 to provide thermal energy to a material P to be heated comprises a heating body 2 having a basic constituting body, which is constituted of an electrically insulating substrate 2a and resistant heat generators 2b, 2c formed on the substrate and generating heat by current carrying, and a first and a second heat transmitting members 3, 4 so installed as to sandwich the heating body 2 and having higher thermal conductivity than that of the substrate 2a of the heating body.