A fabrication method for a flexible circuit board is provided. The fabrication method includes the following steps. Firstly, a release film having an upper surface and a lower surface opposite to each other is provided. Next, two flexible substrates are respectively disposed on the upper surface and the lower surface. Next, a plurality of nano-scale micro-pores are formed on each flexible substrate to form two non-smooth flexible substrates. The nano-scale micro-pores evenly distributed over an outer surface of each non-smooth flexible substrate. Each non-smooth flexible substrate being adapted to be performed a plating process directly on the outer surface thereof.