Abstract: An infrared sensor includes a first emitting module, a second emitting module, and a receiving module. The first emitting module includes a first emitter and a first lens; the second emitting module includes a second emitter and a second lens. The first emitter and the second emitter respectively emit an infrared ray along an optical axis, wherein an acute angle is formed between the optical axes. The receiving module is located between the first emitting module and the second emitting module, wherein the receiving module includes a receiver and a third lens. The infrared rays emitted from the first and the second emitter respectively pass through the first and the second lens, afterwards, the infrared rays are reflected to pass through the third lens, and thus received by the receiver. Additionally, the infrared sensor may be applied to a sensor faucet for controlling a water valve in the sensor faucet.