A biosensor is provided. The biosensor includes a substrate, a first photodiode, a second photodiode, an angle-sensitive filter, and an immobilization layer. The first photodiode and the second photodiode are disposed in the substrate and define a first pixel and a second pixel, respectively. The first pixel and the second pixel receive a light. The angle-sensitive filter is disposed on the substrate. The immobilization layer is disposed on the angle-sensitive filter.