An optical waveguide sensor for glucose measurement comprises a substrate, a
first
optical waveguide layer formed on a surface of the substrate, an entrance grating
and an exit grating which are formed contacting with the first optical waveguide
layer and being spaced from each other, a second optical waveguide layer located
between the entrance grating and the exit grating while being in contact with the
first optical waveguide layer, the second optical waveguide layer having a higher
refractive index that that of the first optical waveguide layer, and a functioning
layer containing an enzyme and a coloring reagent which is formed on the second
optical waveguide layer.
