A fabrication method of a rigid-flex circuit board is described as follows. Firstly, a flexible circuit board and at least a cover layer are provided. The cover layer covers a surface of the flexible circuit board. A protection layer is then formed on the cover layer. Next, a substrate is laminated to the surface of the flexible circuit board. The substrate has a conductive layer and a prepreg disposed between the conductive layer and the cover layer. The prepreg has an opening for accommodating the protection layer. Thereafter, the conductive layer is patterned for forming a patterned conductive layer. Afterwards, the protection layer is removed.