Car ferries, pure car carriers and container ships may suffer from slamming on the stern flare because those ships require broad deck plane and the bottom of near the aft part becomes flat. In the present paper, a response of a container ship to stern flare slamming is studied using the numerical method which authors developed to analyze the dynamic response of ship hulls to the impulsive hydrodynamic force. The calculations are performed for the ship in following seas because an environment condition data suggests that a ship is operated in following seas as frequently as in head seas. Results obtained are as follows : 1) When the wave length is equal to the ship length or shorter, there is a possibility of occurrence of severe stern flare slamming. 2) It is recommended from a viewpoint of the strength that stern bottoms should have some degree of dead rise angle. Hydrodynamic impact force is not observed in the calculated result for the ship the stern bottom of which has 10° of dead rise angle. 3) 4- and 5-node vibration have significant influence to the structural response of an aft part of ship as well as 2- and 3-node modes.