Abstract: A dredging method and a dredging apparatus which can efficiently suck large quantities of sand and gravels deposited on the bottom of dams, rivers, harbors, etc., convey them with as much saved energy as possible, and can prevent diffusion of turbid water. To achieve these objects, the apparatus includes a case laid down into the water in communication with the atmosphere. A suction pipe having a suction portion at the lower end thereof is connected to this case. The apparatus further includes a drain pump for draining water in the case and forming a level difference between the water level in the case and the external water level A container is removably disposed at an intermediate portion of the suction pipe. The sand and gravels are sucked from the suction pipe into the container by the siphon principle due to the level difference between the external water level and the water level in the container, and the container is cut off and the sand and gravels are taken out when the container is full.