PURPOSE: To contrive the stabilization of a ship, when it is in sailing, by symmetrically providing a hydrofoil overhung longitudinally to right and left in a submerged part, mounting a movable flap to this hydrofoil and controlling the flap adjusting lift in right and left.

CONSTITUTION: A hydrofoil 2, overhung symmetrically to right and left, is mounted longitudinally at least two parts in both sides of a ship body 1 in a submerged lower part, and a drivable flap 3 is mounted to a rear end of each hydrofoil 2. In the time of sailing, lift is generated in the hydrofoil 2 lowering a draft to LWR from LWS, and a water plane narrows its width decreasing wave making resistance or simultaneously generating unstable rolling by narrowing this width. Then the flap is adjusted in its angle in right and left, ensuring stability. While also pitching is prevented by adjusting the angle of the front and rear flaps 3. Accordingly, a small water plane single-hull ship A, generating small fluid resistance when it is in high speed sailing, can perform stable sailing even in the time of low speed sailing.