An AC pulse arc welding method of the present invention sets an appropriate AC frequency based on a wire feed rate and a polarity ratio when the polarity ratio is changed without changing the wire feed rate to control a heat input to a base material, and sets an appropriate straight polarity current value necessary for one drop per pulse from the polarity ratio and the AC frequency in AC pulse welding. The method makes it possible to achieve appropriate AC pulse welding by setting the polarity ratio, and to easily set the welding conditions.