A dredger comprising a hull, a bucket device (G, G') that can scoop up and excavate sediment on a water bottom, drive means that is provided between the bucket device (G, G') and the hull and moves the bucket device (G, G') underwater, and a sediment transport pipe that transports a sediment excavated by the bucket device (G, G') to a sediment collection location above water, characterized in that the bucket device (G, G') comprises a bottomed tubular main frame (11, 11') that is linked to and supported by the drive means and can be driven horizontally and vertically underwater, a raise/lower body (12, 12') that is formed into a tubular shape having upper and lower ends open and is vertically slidably fitted around an outer periphery of the main frame (11, 11'), a pair of scoop plates (13, 13') that are axially supported on lower end parts of the raise/lower body (12, 12') so that sediment at the water bottom can be scooped up by opening and closing the open lower end of the raise/lower body (12, 12'), an open/close drive device that drives the two scoop plates (13, 13') to open and close, a raise/lower drive device that drives the raise/lower body (12, 12') to be raised and lowered with respect to the main frame (11, 11'), a sand discharge pipe that is fixed within the main frame (11, 11') so as to have one end (Pi) opening on a bottom wall (11b, 11b') of the main frame (11, 11') and have the other end (Po) connected to an upstream end of the sediment transport pipe, and a check valve that prevents reverse flow of the sediment pushed out from the sand discharge pipe toward the sediment transport pipe side, the excavated sediment scooped up by the pair of scoop plates (13, 13') being forcibly pushed into the sand discharge pipe due to the raise/lower body (12, 12') being driven to rise with respect to the main frame (11, 11') in a state in which the scoop plate (13, 13') is closed. characterized in that the bucket device (G, G') comprises a bottomed tubular main frame (11, 11') that is linked to and supported by the drive means and can be driven horizontally and vertically underwater, a raise/lower body (12, 12') that is formed into a tubular shape having upper and lower ends open and is vertically slidably fitted around an outer periphery of the main frame (11, 11'), a pair of scoop plates (13, 13') that are axially supported on lower end parts of the raise/lower body (12, 12') so that sediment at the water bottom can be scooped up by opening and closing the open lower end of the raise/lower body (12, 12'), an open/close drive device that drives the two scoop plates (13, 13') to open and close, a raise/lower drive device that drives the raise/lower body (12, 12') to be raised and lowered with respect to the main frame (11, 11'), a sand discharge pipe that is fixed within the main frame (11, 11') so as to have one end (Pi) opening on a bottom wall (11b, 11b') of the main frame (11, 11') and have the other end (Po) connected to an upstream end of the sediment transport pipe, and a check valve that prevents reverse flow of the sediment pushed out from the sand discharge pipe toward the sediment transport pipe side, the excavated sediment scooped up by the pair of scoop plates (13, 13') being forcibly pushed into the sand discharge pipe due to the raise/lower body (12, 12') being driven to rise with respect to the main frame (11, 11') in a state in which the scoop plate (13, 13') is closed.