The political thriller's takings only dropped by 7%, as it earned another $1.81 million over the weekend.
Elsewhere in the charts, there are three new entries.
Kirsten Dunst and Isla Fisher's comedy Bachelorette enters the standings in second place, while End of Watch, which stars Jake Gyllenhaal and Michael Peña, debuts in third place.
Homegrown comedy Housos vs Authority enters the charts in seventh place.
Affleck, who also stars in Argo, recently admitted that he declined the opportunity to direct the pilot of award-winning political drama Homeland.
The box office top ten for the weekend of November 1 to 4 (all figures in Australian dollars):
1. (1) Argo - $1,813,865
2. (-) Bachelorette - $841,263
3. (-) End of Watch - $738,324
4. (3) Taken 2 - $668,743
5. (2) Paranormal Activity 4 - $649,679
6. (5) The Intouchables - $634,643
7. (-) Housos vs Authority - $526,166
8. (4) Dredd - $434,878
9. (7) Frankenweenie - $431,672
10. (6) Savages - $302,107
Photo gallery - 'Argo' BFI London Film Festival premiere:
Copyright: PA Images Ian West/PA Wire