A circuit breaker, comprising: a trip unit configured to detect an accident current; a switching mechanism configured to separate a moveable contact (121 a) from a fixed contact by receiving a signal indicating the occurrence of an accident current from the trip unit; and a shaft assembly configured to be closed or tripped by the switching mechanism, wherein the shaft assembly comprises: a shaft configured to be rotated by the switching mechanism; a connecting plate coupled to the shaft; a moveable plate rotatably coupled to the connecting plate and having the moveable contact (121 a) for contacting or separating the moveable contact (121 a) from the fixed contact; a latching plate rotatably coupled to the moveable plate, wherein a sliding recess is formed at the moveable plate, and a cam surface (131 b) is formed at the latching plate so as to implement a different opened degree of the sliding recess of the moveable plate when the latching plate is rotated; and a latching spring formed as an elastic spring, wherein one end of the latching spring is fixed by a first latching pin that is coupled to one end of the latching plate, and the other end of the latching spring is fixed by a second latching pin that is inserted into the sliding recess thus to be slidably coupled to the cam surface (131 b) of the latching plate and configured to elastically support the moveable plate so that the moveable plate can maintain a closed status and a tripped status. a trip unit configured to detect an accident current; a switching mechanism configured to separate a moveable contact (121 a) from a fixed contact by receiving a signal indicating the occurrence of an accident current from the trip unit; and a shaft assembly configured to be closed or tripped by the switching mechanism, wherein the shaft assembly comprises: a shaft configured to be rotated by the switching mechanism; a connecting plate coupled to the shaft; a moveable plate rotatably coupled to the connecting plate and having the moveable contact (121 a) for contacting or separating the moveable contact (121 a) from the fixed contact; a latching plate rotatably coupled to the moveable plate, wherein a sliding recess is formed at the moveable plate, and a cam surface (131 b) is formed at the latching plate so as to implement a different opened degree of the sliding recess of the moveable plate when the latching plate is rotated; and a latching spring formed as an elastic spring, wherein one end of the latching spring is fixed by a first latching pin that is coupled to one end of the latching plate, and the other end of the latching spring is fixed by a second latching pin that is inserted into the sliding recess thus to be slidably coupled to the cam surface (131 b) of the latching plate and configured to elastically support the moveable plate so that the moveable plate can maintain a closed status and a tripped status. a shaft configured to be rotated by the switching mechanism; a connecting plate coupled to the shaft; a moveable plate rotatably coupled to the connecting plate and having the moveable contact (121 a) for contacting or separating the moveable contact (121 a) from the fixed contact; a latching plate rotatably coupled to the moveable plate, wherein a sliding recess is formed at the moveable plate, and a cam surface (131 b) is formed at the latching plate so as to implement a different opened degree of the sliding recess of the moveable plate when the latching plate is rotated; and a latching spring formed as an elastic spring, wherein one end of the latching spring is fixed by a first latching pin that is coupled to one end of the latching plate, and the other end of the latching spring is fixed by a second latching pin that is inserted into the sliding recess thus to be slidably coupled to the cam surface (131 b) of the latching plate and configured to elastically support the moveable plate so that the moveable plate can maintain a closed status and a tripped status.