A method of improving soft ground, capable of effectively restricting settlement of a peripheral part of ground to be improved involved in improvement of the soft ground. A vertical supply path is formed by placing a vertical drain material in ground in the periphery of ground to be improved, and water containing a water stop material is charged in the vertical supply path to supply the water containing the water stop material to the ground through the vertical supply path. Then the water stop material charged in the vertical supply path follows a water flow and spreads in the periphery of the vertical supply path to form a water stop zone. The water stop zone formed by the water stop material prevents the movement of ground water in the ground and restricts lowering of the ground water in the ground caused by forced drainage from ground to be improved, effectively restricting settlement of the ground involved in improvement of soft ground.