A process for producing a polymer optical waveguide including: 1)
preparing a rubber mold having a composite layer structure in which a
rubber layer which has a concave portion corresponding to an optical
waveguide core and contains a rubber mold-forming curable resin is buried
in a rubber layer-forming concave portion of a rigid substrate having the
rubber layer-forming concave portion; 2) bringing a cladding substrate
into close contact with the rubber mold; 3) filling the concave portion
of the rubber mold, with which the cladding substrate has been brought
into close contact, with a core-forming curable resin; 4) curing the
filled core-forming curable resin; 5) removing the rubber mold from the
cladding substrate; and 6) forming a cladding layer on the cladding
substrate on which the core has been formed.