The 22-year-old, who claimed team bronze for Great Britain alongside sister Jen earlier this week, shot a perfect 10.9 with her final effort in Changwon to finish on 623.3 points.
Germany’s Isabella Straub won silver - 0.2 points behind - with Slovakia’s Daniela Demjen Peskova a further 0.4 points back.
McIntosh said: “I don’t think I’m quite aware of what it is I’ve done yet.
“Winning a team medal helped me because I wasn’t so nervous today, plus I learned from my match yesterday to allow me to put in a better performance today.
“It was a tough competition. I just tried to work on making today’s performance better than yesterday’s and didn’t really think about the outcome.”