PURPOSE: To sense and track a target quickly even for a case when many targets exist or the tracking gates are overlapping by controlling the gate circuit and opening the gate for high speed sensing when target is to be high speed sensed from the radar image.

CONSTITUTION: Gate circuits 4, 7 open a gate in the position set by a CPU 6. The azimuth and distance data for the circuits 4, 7 is given by an azimuth distance generator circuit 9. When the gate is opened by the circuit 4, the data on the target existing in the gate is accommodated in a memory part 5. When the gate is opened by the circuit 7, on the other hand, a high speed target sensor circuit 8 senses the position and size of the target existing in the gate, and they are given to the CPU 6 as interrupting. The CPU 6 senses, for example at catching in the early stage, the target which has the possibility of collision on the basis of the output of the sensor circuit 8, and thereupon the gate is opened by the circuit 4.