The 17-year-old Shiffrin built on her first-run lead to finish in a combined time of 2 minutes, 1.73 seconds - living up to her billing as American skiing's next big star following her first career World Cup win last month in Are, Sweden.
Frida Hansdotter of Sweden came second, and Erin Mielzynski of Canada was 1.76 behind in third. The rest of the field finished more than 2 seconds off Shiffrin's winning time.
Tina Maze of Slovenia, who was second after the opening run, straddled a gate and failed to finish. Maze lost her lead in the slalom standings to Shiffrin but remained atop the overall World Cup standings.