Surface profiles of beads on plate are theoretically discussed on the basis of surface tensional theory. In the first part of this paper, the theoretical surface profile of molten pool is made clear by using the two dimensional model of molten pool under the following assumptions.(1) The molten pool is long enough in the welding direction (two dimensional model), i. e. the curvature of pool surface along the welding direction is ignored.(2) The arc force, acting on the pool surface, is negligibly small.(3) The surface tension of molten metal is constant all over the pool surface.In the second, the calculated surface profile at the two dimensional molten pool is compared with the bead shape on plate in non shielded arc welding or submerged arc welding with strip electrode. At all over the practical welding conditions, it is consequently clarified that the experimental result is in good qualitative agreement with the calculated one for molten pool.Thus, it is concluded that the two dimensional analysis, based on the simple assumptions, is quite available to foreknow the bead surface shape when three boundary conditions, the bead width, the cross sectional area of deposit and the capillary constant of molten metal, are given. In other words, the two dimensional analysis, used in this work, may be valid for the other positional processes such as horizontal fillet welding and horizontal welding.