A flexible circuit board including at least two electrical conducting layers, at least two non-electrical conducting layers, and at least one adhesion layer is provided. The non-electrical conducting layers are disposed between the electrical conducting layers. The non-electrical conducting layers are adhered together via the adhesion layer. A sum of thickness of the non-electrical conducting layers is greater than 4 mil, and there is no electrical conducting layer sandwiched between the at least two non-electrical conducting layers.