To provide an aluminum alloy for semisolid casting which can be improved in strength as well while ductility is suitably assured and a method for manufacturing a casting.

The aluminum alloy for semisolid casting contains components, such as 4.5 to 6.5mass% silicon, 0.4 to 0.8mass% magnesium, 0.05 to 0.2mass% iron, and 0.01 to 0.2mass% titanium, and composing of the balance aluminum (Al) and inevitable impurities. The casting is manufactured by casting the aluminum alloy for semisolid casting by a semisolid casting process to form an intermediate casing, then subjecting the intermediate casting to a solid solution treatment (for 1 to 5 hours at 490 to 550°C) and an aging treatment (1 to 10 hours at 150 to 190°C).