According to one embodiment, an ultrasonic bonding apparatus includes an ultrasonic transducer, a distal-end tool, an ultrasonic horn and an ultrasonic oscillator. The ultrasonic oscillator includes an oscillation circuit and a control device. The ultrasonic oscillator applies the voltage oscillated by the oscillation circuit to the ultrasonic transducer. The control device is configured to detect a voltage reflection ratio from the voltage and current supplied from the oscillation circuit and to control the frequency of the voltage generated by the oscillation circuit, thereby to minimize the voltage reflection ratio.