The invention refers to a circuit breaker having a cradle, the cradle having terminals to which a power source side terminal and a load side terminal of a breaker body are respectively connected, and configured to accommodate the breaker body. The circuit breaker comprises: an upper shutter and a lower shutter configured to open and close terminals of the cradle; an upper shutter operation link having one end connected to the upper shutter and another end rotatably coupled to a pivot; a lower shutter operation link having one end connected to the lower shutter and another end rotatably coupled to the pivot; and a shutter safety device comprising a coupling unit fixedly-coupled to the pivot, a rotation unit rotatably coupled to the coupling unit, and a link fixing unit provided at one end of the rotation unit, wherein the link fixing unit is configured to restrict rotation of the upper shutter operation link and the lower shutter operation link in a contacting manner, and to allow the rotation of the upper and lower shutter operation links as the contact is released by rotation of the rotation unit only when the breaker body is inserted into the cradle.