Abstract: A three-phase circuit-breaker includes: three circuit-breaking portion tanks that each have a circuit-breaking portion therein and are filled with insulating gas; an operation unit that opens and closes the circuit-breaking portion; and a driving mechanism that transmits driving force of the operation unit to the circuit-breaking portion. The operation unit is composed of a drive motor and a control power unit that outputs an opening/closing command to the drive motor. The drive motor is provided in the vicinity of the driving mechanism. The control power unit is disposed at a place different from the drive motor. The drive motor and the control power unit are electrically connected.