A different materials joint structure includes: an iron member; an aluminum member disposed on the iron member and integrally joined with the iron member; and a sealant disposed between the iron member and the aluminum member. The aluminum member includes a lateral edge section projecting outwardly from the iron member and extending downwardly, the lateral edge section and a surface of a lateral end of the iron member define a concave section therebetween, and the sealant protruding outwardly from a position between lateral sections of the iron member and the aluminum member is held in the concave section.