Abstract: An ultrasonic beam focusing device with a concave surface comprises a cylindrical housing, a circular piezoelectric polymer film curved to have a concave shape relative to an acoustically active surface thereof and having a pair of circular electrodes at two surfaces thereof, for generating an ultrasonic beam focused at a point and for transducing the received ultrasonic beam into electric signals, leads respectively connected to the electrodes, a rigid polyurethane layer formed in tight contact with an electrode inside the housing at the side of an acoustically inactive surface of the piezoelectric polymer film, for absorbing an ultrasonic beam at the side of the acoustically inactive surface and for supporting the piezoelectric polymer film, and an insulating layer formed in contact with an electrode for electrically insulating the electrode.