PURPOSE: To suppress a sectional area of a wing to a small value, provide an allowance of a strength in a component of the wing and prevent damage of the same by mounting a power source for developing a folded wing at an end of a booster rocket, and separating the source from a missile body at the time of separating the rocket.

CONSTITUTION: A developed wing of a guided missile in which a detachable booster rocket is mounted at a tail of a body is folded at the time of containing in a canister. Immediately after it is launched from the canister, a twisted torque stored at a twisted spring 8 is altered to a rotation of a shaft 6 to develop a wing spreading part 5. A booster rocket 2 is separated from a body 1 of the missile after it is burned, and the spring 8 and a holder 9 are simultaneously separated from the body. Thus, the source for developing the wing is not contained in the wing, but mounted at an end of the rocket 2, thereby suppressing a sectional area of the wing of the body to be flown at a high speed to a small value and reducing an air resistance of the wing.