Abstract: The invention concerns an ultrasonic sonotrode having a sealing surface which is intended to come into contact with the material to be processed. To provide an ultrasonic sonotrode, an ultrasonic sealing apparatus and a method of ultrasonic processing, which avoids complicated and expensive positioning of the sonotrode and which nonetheless ensures uniform good quality for the weld seam, it is proposed according to the invention that the sealing surface is of a two-part configuration and the two sealing surface parts are formed by two mutually facing sealing surface portions.