Disclosed is an acoustic signal detector for detecting a target with moving in water. The acoustic signal detector may include a body having a front portion, the front portion having a cross section which becomes gradually narrow and an end formed to have a plane. The plane may be perpendicular to a moving direction of the acoustic signal detector. The acoustic signal detector may further include a plurality of sensor arrays configured to generate sound and detect sound returned by being reflected by a target. The plurality of sensor arrays may be mounted on a side surface of the front portion and on the plane.