A circuit breaker having a cam rotation delaying function, the circuit breaker performing a closing operation and a charging operation, the circuit breaker comprising: a pair of plates spaced apart from each other; a closing spring having one end portion rotatably coupled to each of the plates; a driving lever rotatably installed at each of the plates and connected to another end portion of the closing spring so as to be rotated responsive to compression and extension of the closing spring; a cam rotatably installed at each of the plates and configured to press the driving lever for rotation; a link mechanism having a plurality of links (130a, 130b, 130c) rotatably installed at each of the plates and connected to the driving lever for operation; a movable contact rotatably installed at a side of each of the plates and contactable with a terminal by an operation of the link mechanism; characterised by at least one supplementary cam connected to the cam having a contact groove; and a cam delaying mechanism installed at each of the plates and configured to attenuate a rotational force of the cam due to a restoring force of the closing spring, wherein the cam delaying mechanism comprises: a delay link contacted by the supplementary cam having a supporting portion; a rotation pin inserted into the delay link for coupling the delay link to the plate; a delay spring installed between the delay link and the plate; wherein the supporting portion is insertable into the contact groove and capable of reducing the rotation of the supplementary cam until being slid out of the contact groove. a pair of plates spaced apart from each other; a closing spring having one end portion rotatably coupled to each of the plates; a driving lever rotatably installed at each of the plates and connected to another end portion of the closing spring so as to be rotated responsive to compression and extension of the closing spring; a cam rotatably installed at each of the plates and configured to press the driving lever for rotation; a link mechanism having a plurality of links (130a, 130b, 130c) rotatably installed at each of the plates and connected to the driving lever for operation; a movable contact rotatably installed at a side of each of the plates and contactable with a terminal by an operation of the link mechanism; characterised by at least one supplementary cam connected to the cam having a contact groove; and a cam delaying mechanism installed at each of the plates and configured to attenuate a rotational force of the cam due to a restoring force of the closing spring, wherein the cam delaying mechanism comprises: a delay link contacted by the supplementary cam having a supporting portion; a rotation pin inserted into the delay link for coupling the delay link to the plate; a delay spring installed between the delay link and the plate; wherein the supporting portion is insertable into the contact groove and capable of reducing the rotation of the supplementary cam until being slid out of the contact groove. a delay link contacted by the supplementary cam having a supporting portion; a rotation pin inserted into the delay link for coupling the delay link to the plate; a delay spring installed between the delay link and the plate; wherein the supporting portion is insertable into the contact groove and capable of reducing the rotation of the supplementary cam until being slid out of the contact groove.