An ultrasonic applicator includes an ultrasonic converter accommodated within a converter housing, a first housing, and a second housing. A rear end portion of the first housing is located in the second housing and an inner end portion of the converter housing is located in the rear end portion of the first housing. A length of the rear end portion of the first housing is adjustable. An outer end portion of the converter housing is connected with the second housing via an elastic element, so that a restoring force may be applied on the converter housing by virtue of a movement of the converter housing relative to the second housing.