PURPOSE: To reduce the difference between directionality gains of various directional beams by equalizing the error included in the data using a beam former.

CONSTITUTION: A beam former is configured with a plurality of receiver elements 11 to constitute a received array 10, a means (A/D converters) 12 to sample the output from these receiver elements 11, and a time delay compensator 13 which makes delay compensation for the output of the sampling means (A/D converters) 12. The delayed time is made changeable by the second delay compensator 15 or by the first named delay compensator 13, and the error included in the delay compensation data is equalized. Both configurations will be accepted; a plurality of such second delay compensators 13 are provided for respective receiver elements 11, and one compensator 13 is provided for a plurality of receiver elements 11.