The man was found in a residential area in Råby, Västerås in the early hours of Monday.
He was found with gun wounds across his body, including one in each leg.
"He has been operated on and his condition is now stable, but we are holding him until we have heard from him," Thomas Gustafsson of the local police told the TT news agency.
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The man is still unidentified by police, who are yet to apprehend any suspects.