Before today the 26-year-old's best World Cup result this season had been a fifth-place finish in Rogla on home soil but in reaching the final, Marguc saw of f the challenge of Canada's Matthew Morison.
Marguc, who took gold in the parallel slalom at the 2013 Snowboarding World Championships, reach the final with victories over Italy's Roland Fischnaller, compatriot Zan Kosir in the quarter finals and Austrian Anton Unterkofler in the semi-final.
And having led in the first run by 0.38 seconds over Morison, in his first World Cup final of the season himself, Marguc extended his advantage to 13.47 seconds after the second run.
In earning his first victory, Marguc now rises to third in the overall World Cup standings after four of the 12 events, still behind Fischnaller and Austrian Andreas Prommegger.
Morison's second place moved him up to seventh in the standings whilst Unterkofler, who triumphed in the small final by beating Patrick Bussler, now lies in 11th.