To provide a leak detector for sealed package capable of continuously performing 100% detection in the leak detection of sealed packages.

This device comprises a conveyor belt 3 for continuously carrying a sealed package W having a detecting gas for leak detection sealed therein and a leak detection part 4 provided in the middle of the carrying route of the conveyor belt to detect the leak of the sealed package. The leak detection part comprises a vibration imparting means 5 for vibrating the detecting gas in the sealed package and a gas detecting means 6 for detecting the detecting gas leaked from the sealed package.