To provide a switching mechanism for circuit breaker greatly improved in assembling workability, using a switching mechanism in a prior art to advantage as much as possible, and improved in the yield rate in production.

The switching mechanism includes a unit body formed of a case and a cover structuring an outline of a circuit breaker, a first and a second manual control button type operating members protruded in one part thereof outward from the unit body to perform the turn-on operation and the breaking operation, and a switching mechanism to be operated, being linked with the operating member. A turning member 102 arranged in the unit body freely to be turned between the ON and OFF states, a latch member 104 connected to the turning member 102 by a link 103 so as to be operated, being linked with turning operation of the turning member 102, through the link 103, an operating plate 105 engaged with one part of the latch member 104, and a cross bar 106 always biased by an elastic member 108 in a direction, in which the movable contact point is separated from the fixed contact point, are supported by a nearly U-shape support 107.