A gas circuit breaker (1) includes a rod-shaped fixed arc contact (3), a cylindrical movable arc contact (5) to contact or be separated from the fixed arc contact (3), a heat puffer chamber (20) storing an arc-extinguishing gas to be blown to an arc (30) generated between the fixed arc contact (3) and the movable arc contact (5), and an insulator (15) received within a receiving hole (14) formed in a distal end part of the fixed arc contact (3). An end surface of the insulator (15) on a side of the movable arc contact (5) faces the side of the movable arc contact (5) via an opening end (33) of the housing hole (14), the end surface on the side of the movable arc contact (5) is disposed closer to the inside of the housing hole (14) than the opening end (33) is, and the insulator is made of an ablation material that is vaporized by heat of the arc (30).