A gas circuit breaker includes: a fixed arc contact disposed on an axis of motion, whose tip is directed to one side in a first direction that is parallel to the axis of motion; a movable arc contact that can reciprocate along the axis of motion between a position when in contact with the tip of the fixed arc contact and a position when separated from the tip of the fixed arc contact; and a first permanent magnet and a second permanent magnet as a permanent magnet whose magnetic poles are aligned in a second direction that is a direction perpendicular to the first direction. The fixed arc contact has a shape that is gradually widened in a direction away from the axis of motion from the tip toward another side in the first direction.