A handpiece for an ultrasonic device includes a handpiece main body and a detachable cartridge attached to the handpiece main body. The handpiece main body includes a main body housing, an actuator for axially transferring a transducer, an operating button, and a handpiece main substrate for operating the actuator according to the control of a controller unit, supplying power to the transducer according to on/off operations of the operating button, and receiving a signal detected by the transducer and transmitting the signal to the controller unit. The cartridge includes a cartridge housing, a transducer for generating ultrasound, a guide pin for guiding the transducer, a magnet, a slider for axially moving the transducer along the guide pin, a window for transferring the ultrasound to a patient, and a bellows for isolating liquid contained in the cartridge housing and helping easy transfer of the slider.
