Abstract: An improved printed circuit board has an electrically insulating board which is made of a base containing synthetic resin, and has at least two conductors, one conductor being on one surface of said circuit board and the other conductor being on the opposite surface of the circuit board. At least one hole extends therethrough, and a conductive layer extends through the hole and covers at least part of the surface of the conductors for connecting the conductors on both surfaces of the circuit board through said hole. A filler composed of electrically insulating resin fills the hole and covers the surface of the layer for providing a highly reliable electrical connection between the two conductors on both surfaces of the circuit board.