An optical waveguide, a package board having the optical waveguide, and manufacturing methods thereof are disclosed. The method of manufacturing an optical waveguide includes: forming a first reflective bump and a second reflective bump, which have inclined surfaces formed on sides opposite to each other and which are disposed with a predetermined distance in-between, on one side of a first cladding; forming a core between the first reflective bump and the second reflective bump; and stacking a second cladding over the one side of the first cladding such that the second cladding covers the first reflective bump, the second reflective bump, and the core. With this method, inclined surfaces can be formed by stacking a metal layer on the lower cladding and then selectively etching the metal layer, which can reduce lead time and enable a high degree of freedom in design.