A method for manufacturing a flexible printed circuit board, comprising: providing a flexible printed circuit substrate; defining first through holes and second through holes through the flexible printed circuit substrate; and forming first conductive pillars and second conductive pillars; and defining first grooves by removing a portion of each first conductive pillar and defining second grooves by removing a portion of each second conductive pillar; the first grooves and the second grooves are defined from an outer surface of the flexible printed circuit board on the second conductive pattern layer side to a surface of the second conductive pattern layer away from the first conductive pattern layer; each of the first grooves is aligned with and corresponds to one first conductive pillar, and each of the second grooves is aligned with and corresponds to one second conductive pillar.