In an automatic faucet having a hand sensor S to start and stop discharging water automatically, only hands can be detected accurately without detecting a washbowl (chinaware) and water stream erroneously. The sensor S comprises a light emitter and a light receiver. The directional axis d of a detection region (in which the light emitting region of the light emitter and the light receiving region of the light receiver are overlapped with each other) intersects the discharged water stream, and further the intersection angle between both is adjusted less than 70 degrees, irrespective of the flow rate of the discharged water. The reflected light levels detected by the light receiver are sampled periodically to calculate an average value and a variance value on the basis of at least eight most updated sampled data. Water discharge is started and stopped on the basis of the calculated average value and the variance value.