To obtain a cage rotor of an aluminum alloy casting which has a tensile strength of 10 kgf/mm2 or higher at 150°C, has electroconductivity of 50% IACS or higher at room temperature, and does not cause crack during casting or due to shock.

The cage rotor is made of an alloy comprising 0.2-1.0 wt.% Zr, 0.05-1.5 wt.% Si, 0.1-0.8 wt.% Ag and the balance aluminum; or 0.2-1.5 wt.% Hf, 0.05-1.5 wt.% Si, 0.1-0.8 wt.% Ag and the balance aluminum. The manufacturing method comprises casting the alloy into a die for the cage rotor, and then aging it in the range of 300 to 450°C.