He was apprehended in the Falun area at 9.30 on Thursday.
Preliminary autopsy results on the murder victim found on Monday showed her to be a local girl reported missing last Friday.
According to police, the suspect does not have a record of serious crime.
“Our internal investigation has led us to this man,” police superintendent Sven-Åke Petters told news agency TT.
The murdered girl was last seen around 7pm on Friday. A relative dropped her off at a bus stop in Mora so she could catch a bus to her father in Älvdalen.
But the girl never arrived.
A technical examination of the scene has been completed, resulting in several useful clues, although police do not wish to reveal exactly what they are.
The police also deny claims that a burned out car found in the area has anything to do with the killing.
Investigators said they went through the girl’s computer to see whom she may have contacted, including men contacted via the internet.
What remains perplexing to authorities is that the girl logged in to a popular site for young people, Lunarstorm, shortly before 9 o’clock Saturday morning.
“It’s entirely possible that someone else logged in under the girl’s name. No one is saying that it was actually her who logged in and I can’t say much more than that,” said Petters.
Police were refusing to comment on the autopsy results on Thursday morning, which were expected to show exactly how the girl died and whether she was also the victim of a sexual assault.