According to an embodiment of the present invention, a medical device can comprise: a piezoelectric element for generating ultrasonic waves; a transmission part coming into contact with the piezoelectric element, and transmitting, to the skin, the ultrasonic waves and an electrical stimulation signal generated from the outside; and a guide having a ring shape having an inner surface and an outer surface, and coming into contact with one surface of the transmission part in order to provide a functional material accommodation space. The functional material accommodation space can be defined by the inner surface of the guide and the one surface of the transmission part. According to the present invention, a functional material accommodation space capable of maximizing the area in which a functional material and the skin make contact can be provided, and the configuration of a circuit for generating ultrasonic waves and the configuration of a circuit for generating an electrical stimulation signal can be simplified.