The invention discloses a net sinking device of a fishing net. The net sinking device comprises a cylinder used for being connected with the fishing net, the cylinder is of a cavity structure, the bottom of the cylinder is provided with a water inlet, the top of the cylinder is provided with an air outlet, and the side wall of the cylinder is provided with a water outlet hole communicated with the cavity structure. In this way, the net sinking device of the fishing net is portable and cannot cause great influence on a load of a ship, and in the optimum scheme, the problems that the fishing net is damaged due to concentrated stress points, and a hull or people are likely to be damaged can be avoided.