This paper describes the numerical analysis of the free surface flow near the transom-stern of a ship. The 2D+T method that is a kind of slender body theory was introduced to the ship-wave problem, which was mathematically formulated based on the potential theory. Nonlinear free surface conditions were satisfied at the exact location on the body surface. Such numerical solutions can be obtained using the boundary element method (BEM). The free surface of the hollow cavity region behind the dry transom can be rationally assessed by the computational modeling. Numerical studies were carried out for nine types of transom shape in a wide range of Froude number. The present procedure was found to be effective for the analysis of the wave-making phenomena due to the transom-stern.