The present invention provides an ultrasonic wave generator capable of generating ultrasonic waves of a target driving frequency stably and an ultrasonic cosmetic device using the generator. The ultrasonic wave generator 1 of the present invention comprises a driving section 11 producing electric oscillations, an ultrasonic vibrator 12 converting the electric oscillations from the driving section 11 into mechanical vibrations, a face bonding ultrasonic vibrator 12, an electric horn 13 connected to the ultrasonic vibrator 12 on one side and transmitting the mechanical vibration of ultrasonic waves from the ultrasonic vibrator 12 to the radiating surface on the other side, a measuring section 14 measuring the impedance of the ultrasonic vibrator 12, and a controlling section 15 determining a target driving frequency for driving the ultrasonic vibrator 12 on the basis of the impedance at the intersections between impedance frequency characteristics of the ultrasonic vibrator 12 under a load and those without a load and the impedance measured by the measuring section 14 to control the driving section 11 so that the ultrasonic vibrator 12 vibrates on the calculated target driving frequency. |