I have uninstalled an app from Finder->Applications. But in launchpad, icon of the app still exists. How to remove it?
I've tried to restart Mac, no luck.
You may need to force launchpad to rebuild it's databases. In the Terminal run
rm ~/Library/Application\ Support/Dock/*.db; defaults write com.apple.dock ResetLaunchPad -bool true; killall Dock;
NOTE: this method will re-arrange all of your launchpad icons. – Martin Zhai
Reinstall it and delete it again.
Much easier solution: you have to "long-click", just click and keep it pressed in launchpad. The buttons start to wiggle, the interface is copied from iOS.