Abstract: A switch having a circuit breaker comprising a housing into which an electric current is permitted to enter via a first wire connecting piece before arriving at a neon lamp via a movable piece, a fixation piece, a press tip and a spring. The press tip and a conductive piece are caused by the press key to swing so as to make contact with the fire wire connecting piece and a second wire connecting piece for turning on the neon lamp. When the electric current becomes excessive, a position limiting connection point is caused by a curve piece of a dual metal piece to withdraw from a slot of an insulated board. The insulated board is provided with a neck capable of being restrained by a projection of a housing cover of the housing so as to cause the insulated board to move up to bring about an automatic interruption of the flow of the electric current.