An optical wiring board and a manufacturing method thereof are disclosed. In accordance with an embodiment of the present invention, the method includes providing a base substrate having a wiring groove formed therein, forming a first clad layer by filling a first clad substance in the wiring groove, stacking an intermediate insulating layer on the base substrate, in which the intermediate insulating layer has a first through-hole formed therein and the first through-hole corresponds to the wiring groove, forming a core unit on the first clad layer, stacking a cover insulting layer on the intermediate insulating layer, in which the cover insulating layer has a second through-hole formed therein and the second through-hole corresponds to the first through-hole, and forming a second clad layer by filling a second clad substance in the second through-hole, in which the second clad layer covers the core unit.