A breaker includes conductors, each including an elongated flat cut portion, cutting chambers arranged in correspondence with the cut portions, a single cutting member that includes blades to cut the cut portions in the cutting chambers, a gas generator that generates gas to move the cutting member toward the cut portions, and an arc attenuation portion located between the two cut portions that are adjacent to each other. The conductors are located between two devices. Each cut portion is cut to form two separated cutting ends and electrically disconnect the devices. The arc attenuation portion attenuates an arc generated between the two cutting ends of one of the two adjacent cut portions and the two cutting ends of the other cut portion.