The present invention discloses an LED lens and a light source device using the same. The light source device includes the LED lens and a LED. The LED lens comprises a light incident surface, a light emitting surface, and a bottom surface. The light emitting surface includes a recession portion disposed at the central thereof and a convex portion connected to the recession portion. The light incident surface is a concave surface and comprises a first optically active area and a second optically active area. The first optically active area is disposed at the central of the light incident surface; the second optically active area is connected to the first optically active area and the bottom surface. At the junction between the first optically active area and the second optically active area, it is an optical path inversion point that is disposed satisfying specific condition.