PURPOSE: To prevent a drop in the power of a warhead by providing a mechanism in which a guidance device measures a distance to a target and is separated from other parts when the distance is less than a predetermined value.

CONSTITUTION: A guidance device 1 compares the intensities of reflected waves from a target 6 as received by a beam A and a beam B formed by an antenna built therein to obtain an error angle from the center of the beams while a distance R is obtained from elapsed time to the reception of a transmitted wave. The error angle obtained from the guidance device 1 is sent to a wing control part 4. An airframe advances to reach the target 6 by the action of a guidance system comprising the guidance device 1, the wing control part 4 and a steering wing 5. A separation mechanism 2 houses a spring locked being compressed. The guidance device 1 outputs a separation command, when the distance R measured reaches a preset value. The separation mechanism 2 releases the lock of the housed spring, which inturn, extends to separate the guidance device 1 from the body of the airframe.