Hector Scott, 41, from Kingston, in the Australian Capital Territory (ACT) was charged under section 25 of the Prostitution Control Act which makes the behaviour illegal.
As a public health measure, the ACT health department contacted nearly 500 people known to Scott.
Forty-three of them admitted to having a sexual encounter with him and were urged to be tested for HIV.
Magistrate John Burns said it was impossible to know whether Scott had unprotected sex with any of his clients.
But he said Scott's breach of the prostitution act was very serious because he chose to put others at risk for his own commercial benefit.
Scott pleaded guilty and also revealed he had failed to register himself as a sex worker.
Magistrate Burns sentenced him to two months and 14 days in jail and a two year good behaviour order .
The sentence sends a "disgraceful" message that having sex with an infected person is unsafe, Australia's peak sex workers association says.
The Scarlet Alliance chief executive Janelle Fawkes said the organisation was "appalled" by the decision, saying she was extremely concerned at the possible repercussions after this kind of message.
"Last week, the ACT attorney-general, Simon Corbell, came out and stated that Section 25 should be reviewed and considering current risk in transmission that, in fact, an HIV positive person being a sex worker does not hold a higher risk for the community," Ms Fawkes said.
"But this week, we have a judge in the ACT making an example of a person who was only being a sex worker whilst HIV-positive.
"That sends a clear and cutting message that having sex with an HIV-positive person is unsafe and that is simply not true."
The same activity in NSW and several other states would not be deemed illegal, Ms Fawkes said.