An ultrasonic treatment apparatus treats a part of the body without use of a medical agent. The ultrasonic treatment apparatus includes a treatment vessel, an ultrasonic element, an ultrasonic element driving circuit, and an operation section. The treatment vessel holds a medium and the ultrasonic element generates ultrasonic waves through the medium to decompose the water in the medium to thereby generate hydroxyl radicals. The ultrasonic element driving circuit drives the ultrasonic element. The operation section is used to set sterilization conditions determined by the amount of hydroxyl radicals generated by the ultrasonic waves.