To provide an ultraviolet sterilizing/purifying apparatus which can purify/sterilize all of water discharged from a plurality of water supply ports in a building by installing only one device in the building and can immediately make water suitable as drinking water from raw water such as ground water, spring water, water of a basin, water of rivers or the like on a site such as a construction site, a disaster relief site, a battle site, a trail up a mountain or the like.

The ultraviolet sterilizing/ purifying apparatus is equipped with a vacuum means for reducing the pressure of raw water to the pressure within a predetermined water pressure range not destructing the following ultraviolet sterilizing device, a removing means for removing foreign matter contained in the raw water, a removing means for chlorine or the like for adsorbing/removing chlorine or a chlorine compound contained in the raw water and the ultraviolet sterilizing device for irradiating raw water with ultraviolet rays not only to sterilize the same but also to decompose the water cluster of the raw water to smaller cluster. The apparatus is further equipped with a means for detecting the illuminance of ultraviolet rays emitted from the ultraviolet lamp of the ultraviolet sterilizing device and a means for detecting the crack or the like of the ultraviolet lamp or the protective pipe thereof.