PURPOSE: To provide a packing material without generating welding defects at the welding part of the same area to the sectional area of the base material and to provide a work using the above packing material.

CONSTITUTION: A packing material A is constituted with setting a sunk part 4 at the top end of a plate type base material 1' facing toward the prescribed place from the above top end and composed with a horizontal surface 2 and a side surface 4. And a work B of this invention is composed by using the packing material A that a root gap is formed with this horizontal surface 2 downward by the prescribed dimension from the down surface of one side base material and the side surface 3 about the work constituted by welding the base material and the base material through the packing material.