A circuit breaker includes: a first arc-extinguishing chamber and a second arc-extinguishing chamber that interrupt a current by opening contact points and extinguish an arc during the current is being interrupted; and a connection unit that connects the first arc-extinguishing chamber and the second arc-extinguishing chamber to each other. The first arc-extinguishing chamber and the second arc-extinguishing chamber are connected to the connection unit in such a manner that shaft lines of the arc-extinguishing chambers form an angle of substantially 90 degrees. The first arc-extinguishing chamber is arranged on a side of the connection unit in such a manner that the shaft line thereof is substantially horizontal, and the second arc-extinguishing chamber is arranged on an upper side of the connection unit in such a manner that the shaft line thereof is substantially vertical.