A silicon biosensor and a manufacturing method thereof is provided, the silicon biosensor includes: a light source performing self emission a light detector generating a photoelectric current corresponding to an amount of incident light an optical fiber transmitting the light from the light source to the light detector and a micro fluidic channel adjusting an optical transmission rate of the optical fiber according to an antibody-antigen reaction when the antibody-antigen reaction occurs. The silicon biosensor can be easily integrated or bonded with a silicon electronic device, so that it is possible to manufacture the biosensor with a low price, under mass production.