In a magnetic puffer type gas circuit breaker including an electromagnetic coil through which a current to be interrupted flows during the breaking operation, and an electromagnetic repulsive member which produces an electromagnetic repulsive force in cooperation with the electromagnetic coil and drives movable parts of a breaking portion of the apparatus, the electromagnetic repulsive member is so arranged that the electromagnetic neutral position of the electromagnetic repulsive member within the electromagnetic coil at the time when the breaking portion has been closed deviates on the closing side with respect to the electromagnetic center of the electromagnetic coil. Further, the characteristics of the electromagnetic repulsive forces between the electromagnetic coil and the electromagnetic repulsive member are so set that their absolute values become smaller on the closing side than on the breaking side with respect to the point at which the electromagnetic center of the electromagnetic coil and the electromagnetic neutral position of the electromagnetic repulsive member are coincident.