The disclosed technology is directed to a treatment system comprises a power supply apparatus and a treatment instrument configured to communicate electrically so as to perform an operation on a biological tissue. The treatment instrument includes an end effector that transmits a high-frequency current to the biological tissue. An ultrasonic transducer is disposed in the treatment instrument. The ultrasonic transducer generates ultrasonic vibration when a second electrical energy is supplied. The ultrasonic transducer delivers the ultrasonic vibration to the end effector. The power supply apparatus includes a processor that supplies the first electrical energy to the end effector with a first voltage waveform about which a crest factor is equal to or lower than 1.5 and controls output of the first electrical energy in a manner that the biological tissue is degenerated and coagulated due to flowing of the high-frequency current in the biological tissue with no discharge occurs.
