The present invention relates to an ultrasonic generator for repelling harmful animals. The invention comprises a columnar ultrasonic wave generating body 18 which has a piezoelectric element 16 and a connecting body 22 and a smaller-diameter connecting body 24 each having a reduced diameter, a diaphragm 28 which is in the form of a speaker horn, and a connecting rod 26 which extends from the ultrasonic wave generating body 18 and connects and fixes the diaphragm 28 to an end thereof. The thickness of the diaphragm 28 gradually decreases from the base 34 connected to the connecting rod 26 toward an outer edge of the diaphragm 28 and one or more undulated portions 36 are formed concentrically on the front face of the diaphragm.
