An orphanage in Papua New Guinea's highlands says it has bought a baby in Enga province for about $US124.

The Bible Faith Outreach charity's orphanage director, Rosa Kepo, told Radio Australia's Pacific Beat a woman who had bought the baby boy from his mother sold him to them.

Ms Kepo says she is not sure if it is illegal to sell babies in Papua New Guinea.

She says the orphanage decided to buy the baby to give it a better chance in life.

"The people who bought this baby, they don't have a job. I know that and they would have not looked after the baby and the baby would still be on the streets again, if that baby grew up," Ms Kepo said.

"But otherwise I am sure that the baby would not survive, they would want to resell it again."

The original asking price for the baby was $US32, but the price inflated to $US118 when BFO became involved.

Rosa Kepo says babies are sold regularly in the area.

"It's hard for women to look after babies. Some are very poor, some are high school children who have unwanted babies so that's what they do," she said.

She says if more jobs were created people would not be as likely to sell their babies.

"If there is more jobs created and people can look after their families with a better income then I don't think this would be going on," Ms Kepo said.

"I really want the government to see what I'm doing, because we are raising these children ... so they can do something with their lives, not just going on the streets."