An ultrasonic treatment apparatus (10) includes a transducer assembly (16) which generates ultrasonic vibration, a probe (14) which is detachably mounted to the transducer assembly, and has a treatment-portion (46) which performs treatment of a biological tissue in a distal end portion, and a main-body-unit-assembly (12) to which the transducer assembly and the probe are detachably mounted, and in which the biological tissue is treated with the treatment-portion when an operator operates the main-body-unit-assembly while the probe is amounted. The main-body-unit-assembly includes a treatment-assembly (26) which has an action-portion (134) in a distal end portion facing the treatment-portion of the probe, and a handle-assembly (22) which is detachably mounted to a proximal end portion of the treatment-assembly, and which brings the action-portion into contact with the treatment-portion of the probe or separates the action-portion from the treatment-portion while the handle-assembly is mounted to the proximal end portion of the treatment-assembly.
