Spokesperson Captain Shadow Mashobane said the man was standing in a queue outside the bank when he was allegedly attacked at 9am.
The robbers allegedly stole a briefcase with an undisclosed amount of money and fled in a red BMW, said Mashobane.
"The briefcase was later found abandoned on the outskirts of Meyerton, next to Sicelo informal settlement," he said.
The wounded man was rushed to a local clinic in a serious but stable condition.
Police are investigating a case of attempted murder and armed robbery.