The ad was placed in the Metro newspaper in Gothenburg by a fictional teen looking for sex in the city, The Local.se reported Monday.
Just a few days after the ad was placed, a phone number attached to it had 130 missed calls and seven texts. After a week, the number had received 287 calls and 57 texts.
Local police said they were not surprised by the public interest.
"The fact that you got 130 calls over the weekend doesn't surprise me. For those people keeping an eye on the supply, things get exciting with a new ad," Mats Paulsson, head of the prostitution unit of the Gothenburg police, told the Metro newspaper.
Paulsson said most people were probably more curious than they were interested in buying sex.
"Many people call up because they're tickled by the whole thing. They're satisfied to just call or text," he said.
In Sweden, prostitution is legal, but paying or attempting to pay for sex is not and is punishable by fines.