Abstract: An Al alloy cast product includes 3.2% to 7.2% by weight of Mg and 0.28% to 0.6% by weight of Sc, and has an Fe content and an Si content, each of 0.1% by weight or less. The cast product contains, in the metal texture, 3% by volume or less of Al3Sc particle having a particle diameter of 100 nm or less. In production thereof, an Al alloy melt containing 3.2% to 7.2% by weight of Mg and 0.28% to 0.6% by weight of Sc and having an Fe content and an Si content, each of 0.1% by weight or less, is prepared. Next, a casting formed from the melt is subjected to an aging treatment without a solution heat treatment (or a quenching treatment). Then, 3% by volume or less of Al3Sc particle having a particle diameter of 100 nm or less is precipitated in the metal texture.