An optical waveguide production method is provided which reduces a transmission loss, improves alignment mark visual detectability, and ensures excellent productivity. In the optical waveguide production method, an under-cladding layer, a core and an alignment mark are formed on a surface of a metal substrate. On the other hand, a molding die is prepared which includes a cavity and an alignment mark to be associated with the alignment mark. In turn, light emitted from the side of the molding die is utilized for positioning the metal substrate and the molding die with reference to the pair of associated alignment marks. Then, an over-cladding layer is formed over the core. The alignment mark is formed from a photo-curable composition comprising the following components (A) and (B): (A) a polymerizable composition having a (meth)acrylate group; and (B) a photoradical polymerization initiator.