Abstract: A machine which can automatically make a lengthwise cut in each of the opposite sides of leg shells along the center line in the direction of thickness of the crab legs irrespective of their size, thickness, shape, curve, etc. The machine comprises an upper conveyor belt and a lower conveyor belt, said belts carrying crab legs by holding them therebetween, the lower portion of the upper conveyor belt and the upper portion of the lower conveyor belt being adapted to move vertically symmetrically according to the vertical thickness of crab legs, a pair of circular saws being disposed horizontally movably on the opposite sides of said conveyor belts so that each of said circular saws is at equal distances from the lower portion of said upper conveyor belt and from the upper portion of said lower conveyor belt, each of said circular saws being always given a tendency to move inward.