To provide a reinforced structure of a small boat capable of reinforcing a bottom wall of a hull and obtaining a sinking preventing effect, having a characteristic reinforcing wall reinforcing the bottom wall of the hull manufactured of FRP for the purpose of providing a light, rigid, and small boat difficult to sink if any, and recyclable after disposition, while honeycomb panels are used for right and left side walls, and a bottom wall of the hull in a hull structure of the small boat, and in this case, frames with notches are prepared on both ends, ends of the honeycomb panels are inserted in the notches of the frames, and the inserted portions are jointed by bolts penetrating through the frames.

A reinforcing wall extending in right and left wall directions of a hull and jointed with a bottom wall of the hull is installed inside the hull manufactured of FRP. A synthetic resin foam material under a condition that the reinforcing wall contacts the bottom wall of the hull is installed in a space area formed between an upper wall and front and rear walls of the reinforcing wall.