A methodology for comparative evaluation of the water supply reliability of distribution areas was presented. There are various factors which affect water supply reliability. As they cannot be quantified by the same standard, reliability of water distribution area was examined according to the value of each factor. These factors were organized into an index through the analytical hierarchy process. The reliability of each distribution area of the water supply system in the case study area was comparatively evaluated by the method. The problems and points necessary for improvement of the water supply reliability of each distribution area were indicated.