The unidentified man, in his 40s and from the suburb of Bondi, picked up Aus$1,020,487 (US$770,000) on Monday last week and then scooped another Aus$1,457,834 on Saturday.
"I just thought this is too good to be true," he told NSW Lotteries Monday after being informed of his good fortune.
"The chances of winning twice in such a short period of time must be non-existent. I wish I had some advice to others on how to win the lottery, but I don't."
Asked what he would do with the cash, he said: "I'm not going to be stupid with it." He plans to invest in some Sydney real estate, buy a new car and "a holiday to Honolulu goes without saying".
Lottery organisers could not estimate the likelihood of winning twice in a week, but the odds of winning once are one in 1.845 million.
"We have had people win twice in their lifetime, but not twice in a week. It is very unusual and unique."
Lotteries are hugely popular in Australia, with various government-owned and private-sector operators.
The biggest recent winner was a man from Victoria state who woke up Aus$55 million richer in January.
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