PURPOSE: To provide an Mg-Al alloy die casting member excellent in creep resistance and its manufacturing method.

CONSTITUTION: The grain size is increased to 20 to 160μm, and the metallic structure is formed into a one substantially consisting of an α single phase. Because Mg17Al12 crystallized products unstable at a high temp. are completely melted into the α phase and are disappeared as well as the grain size is increased, its creep resistance is increased and the holding rate of the axial force is improved. Furthermore, the Mg-Al alloy die casting member is subjected to solution heat treatment at 405 to 435°C for 2 to 500hr. The Mg17Al12 crystallized products finely precipitated on the grain boundaries can completely be melted to be made into an α single phase as well as the grain size can be coarsened to 20 to 160μm the objective Mg-Al alloy die casting member excellent in creep resistance can be manufactured.