PURPOSE: To obtain an underwater receiver which has a good S/N (underwater noise ratio to target sound) in a high frequency range by obtaining cardioid directivity by using a universal, inexpensive, and small-sized nondirectional receivers, resistance, capacitor, and operational amplifier.

CONSTITUTION: The nondirectional receivers 2 and 3 are arranged vertically and linearly over and under a nondirectional receiver 1 at specific distance. The output of the nondirectional receiver 2 weighted by a weighting circuit 7a to generates an output 12 while passed through a +90° phase shifter 4 and weighted by a weighting circuit 8a to obtain an output 11. Further, the output of the nondirectional receiver 1 is weighted by a weighting circuit 6 to obtain an output 13. The output of the nondirectional receiver 3, on the other hand, is passed through a -90° phase shifter 5 and weighted by a weighting circuit 8b to obtain an output 15 and also weighted by a weighting circuit 7b to generate an output 14. Further, the outputs 11W15 are inputted to an adder 9 to obtain the output 16 of a directivity generating circuit. When a target sound arrives in a horizontal direction, in-phase and equal-level outputs are obtained from the nondirectional receivers 1W3.