To provide a tabular coil for electromagnetic seam welding which is used in an assembly field such as automobile components and electronic components requiring welding of a metal thin plate such as aluminum and copper, which enhances generation efficiency of high density magnetic flux and enabling accurate welding even if using continuously for long hours, and is capable of application to a metal member of which welding material has not a simple thin plate shape.

This is an electromagnetic seam welding device in which a metal material to be welded is tightened and arranged together with the tabular coil on one side of the flat plate coil provided with a current concentration part of narrow and thin long shape, and the metal material is seam-welded by heat by eddy current and pressing by electromagnetic force generated in the metal material to be welded by the pulse current flowing in the current concentration part. The current concentration part of the tabular coil used in the device is made to have an irregular structure as for the opposite side to the side facing the metal material to be welded, in order to make the value of inductance on the side facing the metal material to be welded smaller than the opposite side does.