A novel flexible circuit board with heat dissipation ability is provided. The flexible circuit board includes a heat sink and a heat spreader having at least one circuit substrate mounted thereon. The heat spreader has a first lower surface and a first upper surface which has a plurality of first grooves formed thereon. At least one platform is formed between two adjacent ones of the first grooves for mounting the at least one circuit substrate. The heat sink has a second lower surface and a second upper surface which has a plurality of second grooves formed thereon and is connected to the first lower surface.