PURPOSE: To enable a configuration to be easy and to maintain an improved line quality without considering a dynamic range of a high-frequency processing system of a receiver of a flying object and suppression of unneeded wave from a ground control station.

CONSTITUTION: An electric wave Wa from a ground control station 10 is transmitted, a response return wave Wb from a rocket R is received, and then a distance L1 and a distance change rate ΔL1 are calculated and measured by a distance/distance change rate measuring device 26. A distance L2 between the rocket R and the ground control station 10 at time T2 where a control command wave Wc which is transmitted after the above calculation and measurement reaches is calculated and a free space loss Lo of the control command wave Wc is calculated according to the distance L2 and a transmission frequency. A computer 32 instructs and controls the amount of attenuation of a variable resistance attenuator so that a reception electric field strength in a receiver of the rocket R reaches a specified preset value based on the free space loss Lo. The calculation and instruction control are made at a plurality of flight positions of the rocket R.