PURPOSE: To provide a water-supply-conduit-line monitoring method wherein it can definitely judge whether leak of water, water hammer and the like have been caused or not even without relying on an especially skilled operator and even when water in large quantities is used at a time as well as its operating property and its safety are improved and to provide its apparatus.

CONSTITUTION: Water-pressure and sound-pressure detection devices 1 and data recording devices 2 are attached to many fire hydrants 34 or the like installed in halfway parts of a water-supply conduit line 33. A water pressure and a sound pressure are detected automatically for many hours and recorded automatically on memory cards. Data on the water pressure and the sound pressure which have been recorded on the many collected memory cards are input to a computer 3, processed an analyzed. Thereby, the water conduit line 33 is monitored.