Disclosed herein is a method of manufacturing a printed circuit board for an optical waveguide which includes electrical and optical layers for transmitting electrical and optical signals to the printed circuit board. The method includes forming a lower clad layer on a base substrate, layering or applying a core material on the lower clad layer, machining a trench in the core material to form a core layer having a core pattern, and forming an upper clad layer on the lower clad layer and the core layer. The method enables an optical waveguide to be manufactured using a simple apparatus and process without the use of an additional photo mask.