Joint structure

A joint structure including a first member made of a metal material, a second member made of a material that is difficult to weld to the first member, and a third member made of a filler material and welded to the first member, the first member, the second member, and the third member being joined together,

• the second member including a through-portion penetrating toward the first member,
• the third member being arc welded to the first member through the through-portion,
• wherein a surface of the first member and a surface of the second member directly overlap each other in an overlapping direction,
• the third member being melted so as to form a flange at a peripheral edge of the through-portion on a surface of the second member which is opposite to the surface of the second member that directly overlaps the surface of the first member,
• at least one of the overlapped surfaces of the first member and the second member including a recess formed into a space separate from the through-portion, the recess being recessed so as to surround an entire periphery of the through-portion,
• the recess being provided with a sealing material for closing a gap between the overlapped surfaces of the first member and the second member,
• the recess being formed into a space separate from a welded part that is a welding site where the first member and the third member are welded together to avoid contact between the third member and the sealing material, the recess being recessed so as to surround an entire periphery of the welded part,
• at least a part of the recess is open so as to face in a direction which intersects with the overlapping direction of the first member and the second member, and
• a size of an open side of the recess is different on opposite ends of the recess.