Abstract: The present invention relates to an Mg—Al—Ca based master alloy for Mg alloys and to a production method therefor, and concerns an alloying master alloy used for magnesium or magnesium alloys. To this end, a feature of the invention is that, while the Ca:Al ration in the composition is maintained at between 7:3 and 1:9, based on percentages by weight in the alloy, a balance of Mg is added in an amount of up to 85% of the entire weight of the master alloy, based on percentage by weight. The production method comprises the steps of: preparing components of a master alloy by selecting a composition in which, while the Ca:Al ration in the composition is maintained at between 7:3 and 1:9, based on percentages by weight in the alloy, there is a balance of Mg in an amount of up to 85% of the entire weight of the master alloy, based on percentage by weight; sequentially melting Mg, Al and Ca; completely melting the components by applying an adequate amount of heat; and rapidly cooling the molten pool.