When the waves generated in bow region traveling along a long slender-body, they meet deformation at middle body region. This phenomenon is difficult to explain by the classical wave-making theory. So far, the deformation of ship wave has been observed by many researchers, and this is known as sheltering effect of body. In this paper an attempt for analysing the ship wave deformation is made under the assumption that the wave number v (ratio of gravitational effect to dynamical effect) is of order 0 (ε^-1). The assumption means the waves generated by bow part are of the same order as the beam of ship. The problem is solved by the method of matched asymptotic expansions using slender-body theory. Incidentally, it becomes clear that as far as the diffraction of ship waves near a slender-body concerned, there are no differences between steady and unsteady ship motions. This is true under the condition that wave length is of the same order as beam. So, the near-field problem coincides with that of Faltinsen's¹⁾. The result obtained here can explain qualitatively the phenomena which have been discovered in the experiments on an extremely slender-body²⁾.