A first bonding material composition according to the present invention is a bonding material composition used when aluminum nitride sintered bodies containing a rare-earth metal oxide are bonded to each other, in which the bonding immaterial composition contains, in addition, to an O element-containing aluminum nitride raw material, (a) as a fluorine compound, at least one of a fluorine compound of an alkaline-earth metal and a fluorine compound of a rare-earth metal, or (b) as a fluorine compound, at least one of a fluorine compound of an alkaline-earth metal and a fluorine compound of a rare-earth metal, and a rare-earth metal oxide.