We studied the dependence of sedimentation process in a flocculated kaolinite suspension on the diameter of cylindrical container in the measurement and volume fraction of clay in the suspension. The obtained results were as follows. The constant velocity in the slow settling process depends on the container diameter. In large containers (D=21.3, 28.2, 63.5 mm), it becomes lager as the container diameter increase. This phenomenon can be explained on the basis of a theory focusing on wall stress. However, there exists hardly difference in settling velocity among the small containers (D<13.9 mm) and the very slow sedimentation regardless of the container diameter causes. It is guessed that this phenomenon occurs by the flow which doesn't depend on the container diameter. On the other hand, the maximum settling velocity in the rapid settling process was almost constant regardless of container diameter. From this result, it became clear that the container diameter did not affect on the rapid settling process.