An optical waveguide production method for producing an optical waveguide comprising the steps of: forming an under-cladding layer and an alignment mark from the same material on a substrate; forming a thin metal film on the alignment mark; forming a first transparent photosensitive resin layer on the resultant substrate to cover the under-cladding layer and the thin metal film; positioning an exposure mask with reference to the thin metal film formed on the alignment mark; and selectively exposing a predetermined portion of the first photosensitive resin layer on the under-cladding layer via the exposure mask to form a core defined by the exposed portion of the first photosensitive resin layer.