PROBLEM TO BE SOLVED: To provide a seaweed culturing device for culturing seaweed on land.SOLUTION: Water flow adjustment mechanism comprises roughly truncated cone shaped cylindrical member 5 having openings on its top part and bottom part. The cone shaped top part opening of the cylindrical member 5 is located on the bottom part of a cylindrical water tank 2. The cone shaped bottom part opening of the cylindrical member 5 is located on the upper opening part side of the cylindrical water tank 2. The cone shaped central axis is arranged so as to be roughly coinciding with the central axis of the cylindrical water tank 2. The water flow adjustment mechanism comprises a plurality of opening in the upper and lower direction on its peripheral surface. A water injection mechanism 3 is arranged so that its water injection port is close to the inner peripheral edge of the cylindrical water tank 2 and its water injection direction is roughly coincided with the tangential direction of a section of the cylindrical wat
