The disclosed water purifier comprises an outer wall, a RAW water inflow section that allows inflow of RAW water from outside said outer wall, a purifying section, an ultraviolet ray sterilizing section that has an ultraviolet ray source, a purified water outflow section that allows purified water that has been purified in said purifying section and sterilized in said ultraviolet ray sterilizing section to flow to the outside of said outer wall, a condition-detecting unit, and a control unit that controls generation of ultraviolet rays from said ultraviolet ray source according to the detection by said condition-detecting unit.