PURPOSE: To facilitate signal processing by allowing a secondary radar antenna to make a scan at shorter scan intervals than a primary radar in synchronism with the azimuth-directional election scanning of the primary radar.

CONSTITUTION: The secondary radar antenna 7 is installed at the same place with the primary radar antenna 1 and a signal processor 3 controls the primary and secondary radars and performs reception processing. Then the processor 3 generates a direction signal which is narrower in scanning interval than the primary radar in synchronism with the azimuth-directional electron scanning of the primary radar device for the secondary radar and a control part 8 supplies a phase signal required for desired beam pattern formation to an antenna 7. Consequently, the same azimuth scanning intervals with mechanical rotation are obtained and the time lag between the primary radar and secondary radar is small, so the correlation between the both is easily obtained and the load on the signal processor is never increased.