A circuit breaker is shown which includes a plurality of fixed contacts and a plurality of corresponding movable contacts. An actuating shaft is operatively connected to and actuates the plurality of movable contacts to couple with/separate from the corresponding fixed contacts. A supporting device for the actuating shaft can be movably connected to a wall of the circuit breaker, and the actuating shaft can be operatively coupled to the supporting device to rotate around a rotation axis relative to the wall of the circuit breaker and the supporting device itself. The circuit breaker can include an adjustment device for adjusting at least the position of the actuating shaft relative to the wall.