An LED unit includes an LED and a lens mounted on the LED. The lens includes a light-incident face adjacent to the LED, a light-emergent face remote from the LED, and a light-reflecting face between the light-incident face and the light-emergent face. The light-incident face includes a first light-incident face facing the LED, and the light-emergent face includes a first light-emergent face located opposite to the first light-incident face. The first light-incident face is a continuously curved face which has a curvature, along a bottom-to-top direction of the lens, firstly decreasing gradually to a first value; then increasing gradually to a second value; then decreasing gradually again to a third value; and then increasing gradually again. The light-emergent face has a first light-emergent face located above the first light-incident face and having a varied curvature.