To provide a water supply cutoff pipe line searching method capable of more realistically searching a water supply cutoff section of a water service pipe line by taking a physical connecting state of the water service pipe line but also hydraulic effect into consideration.

First of all, water service pipe lines 14 and 18 not wider than a predetermined caliber forming a water service pipe line network are once excluded, it is confirmed whether or not other water service pipe lines are connected to the water service pipe lines in a circulation state, and the water supply cutoff state of the water service pipe line is primarily searched. Then, the water service pipe lines 14 and 18 not wider than the predetermined caliber once excluded are again revived, and it is confirmed whether or not the water service pipe lines 14 and 18 not wider than the predetermined caliber are connected to the water service pipe lines in a circulation state to finally search the water supply cutoff state of the water service pipe line.