The man from Skaraborg on Sweden's west coast, who is now 20, admitted that he had sex with the girl on several occasions but denied it was a criminal offence.
He argued in the district court that when the intercourse took place in 2010, the age difference between the two seemed insignificant. In Sweden the legal age of consent is 15 years old.
However, his argument didn't stand up in court, where he was convicted for having had sex with a minor and put on probation on a charge of sexual exploitation according to the Skövde Nyheter newspaper.
The district court said it was clear the man had sexual relations with the girl and told him to undergo treatment. He was also ordered to pay 5,000 kronor ($770) in damages to the girl .
Last year former minister Thomas Bödstrom, who helped push through tougher legislation on sex laws in 2005, said Swedish courts were interpreting the law wrongly on occasion.
"(The law) exists so that older people can't abuse children under the age of 15, and it's really important that we keep them protected. But this has not taken into account two young people who have completely consensual sex with one another," Bodström told Sveriges Radio (SR).
If, for example, a 15-year-old were to have consensual sex with a 14-year-old partner, the older teen could nevertheless risk being convicted of sexual assault, rape, or exploitation of a minor.
In 2007, the Swedish Supreme Court didn't hand out a sentence in a case where sex took place between a 17-year-old and a 14-year-old where it was argued that it was consensual.
At the time the intercourse took place in the 2007 case the girl was 14 years and seven months old, but similar trials have not followed the same path according to to Åsa Regnér, head of Sweden's National Association for Sexuality Education (RFSU).
"This has drifted into being a kind of moral issue as to whether the young people should have sex or not, and we think that's a question for them to decide, as well as their parents," she told SR in 2012.
She added; "Whether others have a moral issue about it is up to them, but it shouldn't result in it being taken to our courts and being a question for police and prosecutors."